THE SEROTONIN TRANSPORTER GENE AND PERSONALITY: ASSOCIATION OF THE

THE SEROTONIN TRANSPORTER GENE AND PERSONALITY:

ASSOCIATION OF THE 5HTTLPR S ALLELE, ANXIETY, DE-PRESSION AND AFFECTIVE TEMPERAMENTS

PhD thesis

XENIA GONDA

National Institute of Psychiatry and Neurology Laboratory of Neurochemistry and Experimental Medicine

Semmelweis University

PhD School of Mental Health Sciences

Témavezető: Prof. Dr. Bagdy György SZIGORLATI BIZOTTSÁG ELNÖKE: Prof. Dr.Tringer László SZIGORLATI BIZOTTSÁG TAGJAI: Prof. Dr. Török Tamás Dr. Lévay György BÍRÁLÓBIZOTTSÁG ELNÖKE: Prof. Dr.Tekes Kornélia BÍRÁLÓBIZOTTSÁG TAGJAI: Prof. Dr. Oláh Attila Dr. Molnár Mária Judit Dr. Németh Attila Dr. Kéri Szabolcs HIVATALOS BÍRÁLÓK: Prof. Dr. Janka Zoltán Dr. Tolna Judit

Budapest 2007.

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THE SEROTONIN TRANSPORTER GENE AND PERSONALITY: ASSOCIATION OF THE 5HTTLPR S ALLELE, ANXIETY, DEPRESSION AND AFFECTIVE TEMPERAMENTS 1 1. ABBREVIATIONS 4 2. INTRODUCTION 6 3. LITERATURE OVERVIEW 6 3.1 THE SEROTONERGIC SYSTEM 6 3.2 THE SEROTONIN TRANSPORTER 11 3.2.1 PHARMACOLOGY OF THE SEROTONIN TRANSPORTER 12 3.2.1.1 Selective serotonin reuptake inhibitors 12 3.2.1.2 Other antidepressive agents 14 3.2.2 GENETICS OF THE SEROTONIN TRANSPORTER 15 3.2.3 THE 5HTTLPR POLYMORPHISM 17 3.2.4 PHARMACOGENETICS OF THE SEROTONIN TRANSPORTER GENE 23 3.3 TEMPERAMENT 24 3.3.1 EARLIER MODELS OF TEMPERAMENT 24 3.3.2 CLONINGER’S MODEL OF TEMPERAMENT 25 3.3.3 AKISKAL’S MODEL OF AFFECTIVE TEMPERAMENTS 26 3.4 NEUROTICISM 29 3.4.1 NEUROSIS 31 3.5 DEPRESSION 35 3.5.1 SUBTHRESHOLD AND SUBCLINICAL FORMS OF DEPRESSION 36 3.5.2 NEUROBIOLOGICAL BASIS OF DEPRESSION 39 3.5.2.1 Neuroanatomy of depression 39 3.5.2.2 Neurotransmitters 41 3.5.2.3 Neuroendocrine function 43 3.5.2.4 Neurotrophic factors 44 3.5.3 GENETIC BACKGROUND OF DEPRESSION 45 3.6 ANXIETY 46 3.6.1 NEUROBIOLOGICAL BASIS OF ANXIETY 47 3.6.1.1 Neuroanatomy of anxiety 48 3.6.1.2 Neurotransmitters mediating anxiety 49 3.6.2 GENETIC BACKGROUND OF ANXIETY 51 4. OBJECTIVES 52 5. METHODS 53 5.1 SUBJECTS AND MEASURES 53 5.1.1 GENERAL ASPECTS 53 5.1.2 INVESTIGATION OF THE ASSOCIATION BETWEEN THE 5HTTLPR S ALLELE AND SUBTHRESHOLD DEPRESSION 54 5.1.3 INVESTIGATION OF THE ASSOCIATION BETWEEN THE 5HTTLPR S ALLELE AND ANXIETY 54 5.1.4 INVESTIGATION OF THE ASSOCIATION BETWEEN THE 5HTTLPR S ALLELE AND AFFECTIVE TEMPERAMENTS 55 5.2 GENOTYPING 56 5.3 STATISTICAL ANALYSES 57 5.3.1 GENERAL ASPECTS 57 5.3.2 ASSOCIATION OF THE 5HTTLPR POLYMORPHISM WITH SUBTHRESHOLD DEPRESSION AND AFFECTIVE TEMPERAMENTS 57 5.3.3 ASSOCIATION OF THE 5HTTLPR WITH MIGRAINE AND ANXIETY 58

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6. RESULTS 58 6.1 THE ASSOCIATION OF THE 5HTTLPR AND ANXIETY 58 6.1.1 THE DISTRIBUTION OF THE ALLELES AND GENOTYPES IN OUR SAMPLE 58 6.1.2 ASSOCIATION OF THE 5HTTLPR S ALLELE WITH TRAIT AND STATE ANXIETY 58 6.2 ASSOCIATION OF THE 5HTTLPR S ALLELE WITH SUBTHRESHOLD DEPRESSION 62 6.2.1 THE REPRESENTATIVNESS OF THE SAMPLE AND DISTRIBUTION OF ALLELES AND GENOTYPES 62 6.2.2 THE ASSOCIATION OF ZUNG SELF-RATING DEPRESSION SCALE SCORES WITH PHENOTYPE 62 6.2.3 THE ASSOCIATION OF ZUNG SELF-RATING DEPRESSION SCALE WITH GENOTYPE 63 6.3 ASSOCIATION OF AFFECTIVE TEMPERAMENTS WITH THE 5HTTLPR S ALLELE 65 6.3.1 DISTRIBUTION OF ALLELES AND GENOTYPES IN OUR SAMPLE 65 6.3.2 ASSOCIATION OF THE 5HTTLPR WITH AFFECTIVE TEMPERAMENTS WITH PHENOTYPE 65 6.3.3 THE ASSOCIATION OF AFFECTIVE TEMPERAMENT WITH GENOTYPE 69 7. DISCUSSION 69 7.1 THE SEROTONIN TRANSPORTER GENE AND ANXIETY 69 7.1.1 TRAIT AND STATE ANXIETY AND THE S ALLELE 69 7.1.2 THE ASSOCIATION OF ANXIETY, MIGRAINE AND THE S ALLELE 70 7.2 THE SEROTONIN TRANSPORTER GENE AND SUBTHRESHOLD DEPRESSION 71 7.3 THE ASSOCIATION OF THE SEROTONIN TRANSPORTER GENE WITH AFFECTIVE TEMPERAMENTS 72 7.4 THE ASSOCIATION OF THE 5HTTLPR S ALLELE WITH A LOW/ LABILE MOOD HIGH ANXIETY ENDOPHENOTYPE WITHIN A PSYCHIATRICALLY HEALTHY POPULATION 73 7.5 THE SEROTONIN TRANSPORTER GENE AND NEUROTICISM 74 8. CONCLUSIONS 75 9. SUMMARY 77 9.1 SUMMARY 77 9.2 ÖSSZEFOGLALÁS 79 10. REFERENCES 81 11. PUBLICATIONS 106 11.1 PUBLICATIONS RELEVANT TO THE DISSERTATION 106 11.1.1 JOURNAL ARTICLES 106 11.1.2 POSTERS AND PRESENTATIONS: 107 11.2 OTHER PUBLICATIONS 110 11.2.1 JOURNAL ARTICLES 110 11.2.2. POSTERS AND PRESENTATIONS 111 11.3 BOOK CHAPTERS 114 12. ACKNOWLEDGEMENT 115

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1. ABBREVIATIONS

5HIAA – 5-hydroxy-indoleacetic acid

5HT – serotonin

5HTT – serotonin transporter

5HTTLPR – serotonin transporter length polymorphic region

ANOVA – analysis of variance

AVP – arginine-vasopressine

bp – base pair

BDNF – brain derived neurotrophic factor

CCK - cholecystokinin

COMT – cathechol-o-methyl-transferase

cREB – cAMP response element binding protein

CRF – corticotropin releasing factor

DRD4 – dopamine D4 receptor

DST – dexamethasone suppression test

HPA – hypothalamic-pituitary-adrenal

KO – knock out

LHPA – limbic-hypothalamic-pituitary-adrenal

MHPG – 3-methoxy-4-hydroxyphenylglycol

MAO – monoamino-oxydase

NASI – noradrenalin selective inhibitors

NaSSA – noradrenergic and specific serotonergic antidepressant

NDRI – noradrenalin / dopamine reuptake inhibitors

NEO-PI-R – NEO Personality Inventory Revised

NPY – neuropeptid Y

OCD – obsessive-compulsive disorder

pACC – perigenual anterior cingulate cortex

PCR – polymerase chain reaction

PFC – prefrontal cortex

RFLP - restriction fragment length polymorphism

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rh5HTTLPR – rhesus 5HTTLPR

SARI – serotonin reuptake inhibitor and5HT2 blocker

SLC6A4 – serotonin transporter gene

SNP – single nucleotide polymorphism

SNRI – serotonin / noradrenalin reuptake inhibitor

SSRI – selective serotonin reuptake inhibitor

SubD – subclinical depression

TCI – Temperament and Character Inventory

TEMPS-A – Temperament Evaluation of Memphis, Pisa, Paris and San Diego

TPH – tryptophan hydroxylase

TPQ – Tridimensional Personality Questionnaire

UTR – untranslated region

VNTR- variable number tandem repeats

ZSDS – Zung Self-rating Depression Scale

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2. INTRODUCTION

The serotonin transporter (5HTT) has been proven to play a crucial role in the

background of mood and anxiety disorders. Besides pharmacological evidence, genetic

association studies also point towards this conclusion. Fewer studies, however, have

been carried out to investigate the relationship between the 5HTT gene and psychologi-

cal traits and phenomena within a psychiatrically healthy population. In several studies

it has been described that the s allele of the 5HTTLPR polymorphism of the serotonin

transporter gene has been associated with the neuroticism trait in healthy subjects. Both

the neuroticism trait and psychiatric disorders are very complex both in their manifesta-

tion and in their neurobiological background, with several, mutually interrelated ge-

netic, neurochemical, psychological and social factors playing a role. Therefore, to have

a better understanding of what role the 5HTTLPR polymorphism plays in the back-

ground of mood disorders and anxiety disorders on one hand, and in the background of

the neuroticism trait on the other, it seems more reasonable to find better described,

more distinct and atomic entities composing these phenomena, so that the contribution

of the serotonin transporter gene in the manifestation of psychological characteristics

and psychiatric disorders, and the role of these psychological characteristics in the

background of psychiatric disorders can be outlined and described more precisely.

3. LITERATURE OVERVIEW

3.1 The serotonergic system

The serotonergic system plays a role in the regulation of the activity of the cen-

tral nervous system at several levels and influences a wide variety of physiological and

psychological processes (Lieben, 2004). In the central nervous system, 5-HT fibres are

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widely distributed (Paxinos, 1995; Tohyama and Takatsui, 1998). Cells producing 5-HT

are found in raphe nuclei groups which exist from the midbrain to the medulla oblon-

gata. These areas are classified into nine regions (B1-B9). (B1 – raphe pallidus, B2-

raphe obscurus, B3 – raphe magnus, B4 – central grey matter of medulla oblongata, B5

– pontine medial raphe, B6 – pontine dorsal raphe, B7 – midbrain dorsal raphe, B8 –

caudal linear nucleus, B9 – medial lemniscus). The rostral groups of 5-HT neurons (B5-

B9) give rise to almost all ascending fibres to the forebrain, whereas the caudal groups

(B1-B4) give rise to the majority of descending fibres to the spinal cord (Paxinos, 1995;

Tohyama and Takatsui, 1998).

The dorsal raphe nucleus has two ascending pathways to the cerebral cortex.

One originates from the anterior part of the dorsal raphe nucleus, passing through the

lateral part of medial forebrain bundle and external capsula, and reaching the cortex.

The other pathway originates from the posterior part of the dorsal raphe nucleus, as-

cending within the median forebrain bundle, ascending dorsally at the diagonal band,

and reaching the cingulate gyrus. There are projection pathways for other neurons in the

dorsal raphe nucleus that connect to wide areas in the midbrain such as the thalamus and

hypothalamus to the lateral geniculate body among others (Paxinos, 1995; Tohyama and

Takatsui, 1998)

The 5-HT containing fibres originating from the median raphe nucleus (B8) pro-

ject to areas such as the limbic system, the hypothalamus and hippocampus through the

median forebrain bundle. The descending pathways from the raphe magnus (B3) and

from the raphe obscurus and raphe pallidus (B2, B1) project mainly to the spinal cord,

the former passing through the dorsal part of the lateral column and the latter through

the ventral column (Paxinos, 1995; Tohyama and Takatsui, 1998). Serotonergic projec-

tions are very divergent, each serotonergic neuron is thought to influence about 500000

target neurons (Dahlström and Fuxe, 1964; Steinbusch, 1984; Takeuchi, 1988; Murphy

et al., 1989; Murphy et al., 1991, Baumgarten and Grozdanovic, 1999).

Serotonin is a biogenic amine neurotransmitter, occurring in the central nervous

system but also in the adrenal medulla, the gastrointestinal tract and in platelets (Zifa

and Fillon, 1992). Serotonin is one of the oldest known biogenic amines, first discov-

ered more than 50 years ago in smooth muscle endplates (Amin et al., 1954; Sorensen et

al., 1993). During the time of its discovery it was first known for its vasoconstrictory

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effects and as a promoter of thrombocyte aggregation. In the following years its role as

a central nervous system neurotransmitter has also been described (Amin et al., 1954).

Serotonin plays a central role in the regulation of several processes, such as feeding

behaviour (Blundell, 1977), sexual function (Meston and Gorzalka, 1992), thermoregu-

lation (Myers, 1980), motor activity (Jacobs and Fornal, 1993), neuroendocrine regula-

tion (Montagne and Calas, 1988), memory, learning (McEntee and Crook, 1991), sleep-

wake cycle (Wamsley et al., 1987), pain (LeBars, 1994), aggression (Coccaro, 1992),

impulsivity (Coccaro, 1992), anxiety (Soubrie, 1988), and mood (Maes and Meltzer,

1995). Due to its complex role in the regulation of the above processes it is not surpris-

ing that the role of serotonin has been discovered in the background of several mental

disorders, such as affective disorders, anxiety, eating disorders, obsessive-compulsive

disorder, panic disorder, and schizophrenia (Murphy et al., 1989). Many of the pharma-

cologic agents used in the treatment of these disorders also act through the modulation

of the serotonergic system (Murphy et al., 1989).

Serotonin is synthesised from the essential amino acid tryptophan. Unlike sero-

tonin, tryptophan can cross the blood-brain barrier. For the carrier, however, it has to

compete with other large neutral amino acids, which determines tryptophan uptake and

availability to the brain. In the brain, tryptophan is hydroxylated in the rate limiting step

of serotonin synthesis by tryptophan monooxygenase yielding 5-hydroxy-tryptophan,

which is subsequently transported to the axon nerve terminals and decarboxylated into

serotonin by the aromatic amino acid decarboxylase (Lieben, 2004). After release

from serotonergic neurons, the majority of serotonin is reuptaken through an active

mechanism by the serotonin transporter which leads to the termination of the signal.

Serotonin is catabolysed by the mitochondrial enzyme monoamino oxidase-A into 5-

hydroxy indoleacetic acid (Lieben, 2004).

Our knowledge of serotonin and the serotonergic system has been widening ever

since its first discovery. Serotonin plays a role in several complex mechanisms in the

brain, many of which has been controversial and contradictory, but has been resolved

after the discovery of the different receptors types and subtypes in the serotonergic sys-

tem. At this point there are 18 serotonergic receptors known with different structures,

function and anatomic location. Serotonergic receptors are grouped into 7 classes or

families, denoted by numbers. Receptors in classes are grouped into subclasses accord-

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ing to their pharmacologic characteristics, molecule structure, or transduction mecha-

nism, denoted by letters (Hoyer et al., 1994). The number of these subtypes is increas-

ing, also due to the discovery of isoforms of genes encoding for the receptors (Table 1).

TABLE 1. Classification of serotonergic receptors

RECEPTOR LOCATION FUNCTION CHROMOSOME STRUCTURE TRANSDUCTION

MECHANISM / ACTION

Presynaptic (Dorsal and median raphe)

Thermoregulation Anxiety Sexual behaviour

5-HT1A

Hippocampus Lateral septum Amygdala Cortical limbic area Frontal cortex Entorhinal cortex Brain stem Spinal chord

Depressed mood Aggression Cardiovascular function Memory / learning Muscle spasm Tremor Ataxia Delirium

5q11.2-13 422 amino acids, 7 transmembrane

sequences

5-HT1B 6q13 390 amino acids, 7 transmembrane

sequences

5-HT1D

Substantia nigra Globus pal-lidus Superior col-liculus Caudate puta-men Central grey area Nucleus ac-cumbens

Locomotion Thermoregulation Anxiety Depression Migraine Inflammation Vasodilatation 1p34.3-36.3

377 amino acids, 7 transmembrane

sequences

5-HT1E

Caudate puta-men Basal ganglia Amygdala Hippocampus

6q14-15 365 amino acids, 7 transmembrane

sequences

5-HT1F Cortex Dorsal raphe nucleus

3p12


sequences

Gi/o

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RECEPTOR LOCATION FUNCTION CHROMOSOME STRUCTURE TRANSDUCTION

MECHANISM / ACTION

5-HT2A

Peripheral nervous system Basal ganglia Olfactory nuclei Brainstem Neocortex

Endocrine response Motor control Obsession-compulsion Sleep Psychosis / schizo-phrenia Emotion Cognition


sequences

5-HT2B Peripheral nervous system Limbic system

Intestinal function Panic, anxiety Migraine

2q36.3-37.1 481 amino acids, 7 transmembrane

sequences

5-HT2C

Substantia nigra Globus pallidus Cerebral cortex Olfactory tuber-cles

Locomotion Migraine Hypophagia Anxiety

Xq24 458 amino acids, 7 transmembrane

sequences

Gq/11

5-HT3

Peripheral nervous system Entorhinal cortex Amygdala Brain stem Frontal cortex Hippocampus

Nausea / vomiting Eating Intestinal move-ment Anxiety Learning / memory Withdrawal symp-toms

11 478 amino acids, homopentamer

Cation chan-nel,

Na+/K+/Ca++

5-HT4

Peripheral nervous system Heart Globus pallidus

Striatum Nucleus accum-bens Substantia nigra Limbic system

Eating Intestinal function Control of visuo-motor activity

Emotion / mood Learning / memory


sequences Gs

5-ht5A 7q36.1 357 amino acids, 7 transmembrane

sequences Gs

5-ht5B

Cortex Hippocampus Olfactory bulb Cerebellum

Motor control Feeding Anxiety Emotion / mood 2q11-13


sequences Unknown

5-ht6 Limbic struc-tures cortex

Psychosis Emotion / mood Learning / memory

1p35-36 440 amino acids, 7 transmembrane

sequences Gs

5-HT7


sequences Gs

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5-HT1A receptors are both pre- and postsynaptically located. Presynaptically they

act as somatodendritic autoinhibitory receptors. Presynaptic 5HT1A receptors regulate

serotonergic tone of the central nervous system. 5HT1A receptors play a role in the me-

diation of motor activity, mood, cognition and thermoregulation. 5-HT2 receptors play a

role in the regulation of mood, anxiety, body temperature, sexual behaviour, sleep, eat-

ing and psychosis. 5-HT3 receptors are involved in nausea and vomiting, appetite and

gastrointestinal motility and presumably mood, anxiety and cognition.

5-HT4 receptors play a role in motor activity, memory and emotions. The role of 5-HT5,

5-HT6 and 5-HT7 receptors is now being discovered (Hamon et al., 1988, Barnes and

Sharp, 1999, Lieben, 2004).

Besides its regulating role in the adult brain, serotonin also plays a crucial role as

a regulator of morphogenetic activities during early central nervous system develop-

ment, such as cell proliferation, cell migration and differentiation (Azmitia and

Whitaker-Azmitia, 1997; Lesch and Mössner, 1998). The serotonergic system also in-

fluences and regulates the activity of several other neurotransmitter systems which in

part contribute to the diversity of its functions (Lesch and Mössner, 1998).

3.2 The serotonin transporter

After release, the majority of serotonin is reuptaken to the presynaptic seroton-

ergic neuron through an active mechanism by the serotonin transporter (5HTT) leading

to the termination of the signal. The serotonin transporter is a high-affinity, Na+ and Cl-

dependent transporter with 12 transmembrane domains and it is also the target of anti-

depressants, both tricyclic and the newer selective drugs (SSRIs) as well. The transport

mechanism is driven by a Na+/Cl- gradient. The highest density of the serotonin trans-

porter can be found in the area of the raphe nuclei and the serotonergic projection areas

such as the cortex, entorhinal cortex, hippocampus, amygdala, substantia nigra, puta-

men, and hypothalamus (Lieben, 2004). The serotonin transporter protein, and geneti-

cally driven variations in the function of the serotonin transporter protein has been im-

plicated in the background of several psychiatric disorders (Lesch, 1998).

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3.2.1 Pharmacology of the serotonin transporter

Several drugs effective in mood and anxiety disorders act through the modula-

tion of the serotonin transporter. The first effective drugs in the treatment of depression

were the monoamine oxidase inhibitors and the tricyclic antidepressants introduced

more than 40 years ago. These drugs are still considered the standard of efficacy, most

of the drugs developed in the later years are not more effective, only cause less side

effects (Yadid et al., 2000). Both of these groups of drugs influenced the monoaminer-

gic activity of the central nervous system. Tricyclic antidepressants inhibited the reup-

take of monoamine neurotransmitters, but were not selective in their action, (e.g. they

bind with high affinity to various neurotransmitter receptors) which contributed greatly

to their various side effects (cholinergic, adrenergic, histaminergic) besides their thera-

peutic efficacy. The diversity and severity of the side effects of tricyclic antidepressants

lead the way to search for newer, more selective antidepressants. Over the last 40 years,

six other major classes of antidepressants were developed (Yadid et al., 2000): selective

serotonin reuptake inhibitors (SSRI, e.g. fluoxetine, fluvoxamine, citalopram, paroxet-

ine, sertraline), serotonin / noradrenalin reuptake inhibitors (SNRI, e.g. venlafaxine,

duloxetine, milnacipran), serotonin reuptake inhibitor and 5HT2 blocker agents (SARI,

e.g. nefazodone), noradrenergic and specific serotonergic antidepressants (NaSSA, e.g.

mirtazapine), noradrenalin selective inhibitors (NASI, e.g. reboxetine) and noradrenalin

/ dopamine reuptake inhibitors (NDRI, e.g. bupropion). Most of these drugs, among

other effects, influence the reuptake of serotonin by inhibiting the serotonin transporter

(Yadid et al., 2000).

3.2.1.1 Selective serotonin reuptake inhibitors

SSRIs, selective serotonin reuptake inhibitors in therapeutic concentrations in-

hibit the reuptake of serotonin selectively, and thus increase bioavailability of serotonin

in the synaptic cleft (Rosenzweig-Lipson et al., 2007). SSRIs overall are not more effi-

cient than tricyclic antidepressants, but overdosing on these drugs poses less risks, since

they produce less severe side effects (Yadid et al., 2000). SSRIs such as fluoxetine, par-

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oxetine, sertraline, were introduced from the 1980s, and although they managed to de-

crease side effects at the same time as retaining the efficiency of tricyclic agents, still a

significant portion of patients were resistant to treatment, and another part of patients

showed only partial improvement (DeBattista and Solvason, 2003; Thase, 2001).

The inhibition of the serotonin transporter function plays an important role in the

action of almost all antidepressive agents. When the SSRIs were introduced in the

1980s they revolutionalised the treatment of affective and later anxiety disorders

(Rosenzweig-Lipson et al., 2007). SSRIs were among the first psychiatric drugs devel-

oped based on molecular targeting, and thus the effects of these agents were more fo-

cused, resulting in less side effects and greater compliance (Mourilhe and Stokes, 1998).

Since drug choice is based on tolerability and safety almost as much as on efficacy,

SSRIs quickly became popular, since SSRIs are better tolerated also in overdose than

any earlier antidepressants, such as TCAs, heterocyclic antidepressants or MAO-

inhibitors (Mourilhe and Stokes, 1998).

SSRIs, although traditionally are classified as antidepressive drugs, are often

used in the treatment of anxiety disorders as well (Stahl, 2004). By the 1990s SSRIs

became recognised as the first-line treatment medications for several anxiety disorders,

such as obsessive-compulsive disorder, panic disorder, social phobia and posttraumatic

stress disorder, and benzodiazepines became less popular, due to their side effects such

as undesirable sedation, their amnestic effects and the appearance of dependence and

withdrawal symptoms (Stahl, 2004).

It is well known that the activity of the hypothalamus-pituitary-adrenocortical

axis (HPA) is altered in depression leading to cortisol and in some cases ACTH hyper-

secretion (Rota et al., 2005, Chrousos, 1998). It has also been suggested that excessive

cortisol secretion damages the hippocampus leading to decreased inhibition of cortico-

tropin releasing factor (CRF) secretion, which in turn leads to HPA hyperactivity (Rota

et al., 2005). It has also been supported that antidepressants can modulate HPA func-

tion, and there is a hypothesis that the normalisation of HPA activity and clinical recov-

ery are in a causal relationship (Rota et al., 2005). According to some studies, tricyclic

antidepressants (Heuser et al., 1996) and SSRIs (Inder et al., 2001) may have intrinsic

neuroendocrine effects on central HPA axis components and this way inhibit CRF re-

lease and modulate HPA axis hyperfunction (Rota et al., 2005).

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3.2.1.2 Other antidepressive agents

Because SSRIs were only effective in a subpopulation of depressed patients, the

question was raised whether the manipulation of other neurotransmitter systems is also

required to treat depression successfully. Subsequently attention turned to inhibitors of

both serotonin and noradrenalin (SNRI), including venlafaxine, duloxetine and mil-

nacipran, because of their more favourable spectrum of therapeutic effects and increased

therapeutic efficiency (Shelton et al., 2005, Thase et al., 2001). There are, however,

other subgroups of patients, who do not respond adequately either to SSRIs or to

SNRIs, which suggest that other, non-aminergic neurotransmitter systems should also

be taken into account in the treatment of depression (Rosenzweig-Lipson et al., 2007).

Both SSRIs and SNRIs produce side effects due to an increase in noradrenalin and sero-

tonin turnover which nonselectively effects multiple noradrenalin and serotonin recep-

tors (Yadid, 2000). These side effects include agitation, akinesia, anxiety, insomnia,

panic attacks and sexual dysfunction due to the activation of 5HT2 receptors, and gastro-

intestinal disturbances, headache and nausea due to the involvement of 5HT3 receptors

(Nelson, 1997).

Nefazodone (SARI) inhibits serotonin reuptake and blocks 5HT2 receptors at the

same time leading to less side effects and also a possibly faster onset of therapeutic re-

sponse (Stahl, 1997). Mirtazapine (NaSSA) acts by increasing both serotonergic and

noradrenergic neurotransmission by blocking central α2 auto- and heteroreceptors as

well as 5HT2 and 5HT3 receptors, leading to increased serotonin release due to an in-

crease in serotonergic receptor firing and the stimulation of 5HT1 receptors (Stahl, 1997,

Yadid, 2000). Reboxetine (NASI) selectively inhibits noradrenalin uptake leading to the

disappearance of sexual side effects, while bupropion (NDRI) acts through the inhibi-

tion of dopamine and noradrenalin reuptake and is effective particularly in bipolar dis-

order (Yadid, 2000).

The above drugs all facilitate monoaminergic neurotransmission and most of

them inhibit the serotonin transporter protein. Depressive patients can be divided into

subgroups according to which drug is most effective in the treatment of their symptoms.

Studies investigating these drug-depression interactions will probably lead to the better

understanding of the neurochemistry of depression.

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3.2.2 Genetics of the serotonin transporter

The reuptake of serotonin is genetically determined and the expression

and function of the serotonin transporter protein is under complex regulation. There are

variations in the genetic sequence encoding for the serotonin transporter. The expression

of the inherited gene is under physiological influence through several mechanisms in-

volving cAMP, protein kinase C, and tyrosine kinase. After translation the transporter

protein is transformed through various steps of phosphorylation and dephosphorylation

and the final efficiency of the serotonin transporter is defined by its tertiary structure,

i.e. the dimeric and tetrameric configuration (Lesch et al., 1994, 1996). The serotonin

transporter (SLC6A4) gene is a 31 kb long sequence of DNA located on the long arm of

the 17th chromosome (17q11.1-q12). The transporter is encoded by 14 exons in the 3’

end region, while the transcription regulatory region is located towards the 5’ end.

There are several known polymorphisms of the serotonin transporter gene (Fig-

ure 1). Most studies conducted on the genetically based variation of the serotonin trans-

porter function focused on the 5HTTLPR polymorphism, which will be outlined in

more detail below.

In the 5’ untranslated region (5’UTR) there has been a variation de-

scribed due to the alternative splicing of exon 1B and 1C (Lesch and Gutknecht, 2005).

A VNTR (variable number tandem repeats) polymorphism, involving the num-

ber of tandem sequence repeats has been identified in intron 3 (which has earlier been

termed intron 2 before a new upstream intron was identified) with three alleles (Ogilvie

et al., 1996; Lesch et al., 1994; Hahn and Blakely, 2002). This VNTR polymorphism

consists of either 9, 10 or 12 copies of a 16/17 base pair repeat unit. The frequency of

alleles shows a wide variation among different ethnic groups. Results from studies sug-

gest that this VNTR polymorphism is a strong regulator (enhancer) of transcription al-

though it is located outside of coding and promoter regions (Lesch et al., 1994;

MacKenzie and Quinn, 1996). The 12-repeat allele shows greater transcriptional activa-

tion probably due to an increase in the number of transcriptional elements present or the

size difference potentially allowing a more favourable conformation of DNA for bind-

ing transcriptional factors (Hahn and Blakely, 2002). Since this polymorphism may op-

erate as a transcriptional enhancer it consequently also might have a role during brain

16

development and adult synaptic plasticity (Lesch and Gutknecht, 2005). In some studies

this polymorphism has also been found to be associated with unipolar major depression

(Ogilvie et al., 1996), but in general the intron 3 VNTR’s association with affective dis-

orders lead to mixed results (Hahn and Blakely, 2002).

FIGURE 1. Allelic variation in the serotonin transporter gene (Lesch, 2001)

Several other polymorphisms of the serotonin transporter gene were studied but

no consistent results for associations with personality traits or psychiatric disorders have

been described so far. Other polymorphisms in the serotonin transporter gene which

change the structure of the transporter are less investigated, but two SNPs were found to

be associated with OCD and depression (Lesch and Gutknecht, 2005).

A missense mutation resulting in a conserved Ile425Val substitution has also

been found to be associated with OCD. This substitution may modify the α-helical sec-

ondary structure of the transporter protein and eventually transport function, and the

Ile425Val variant may exhibit changes in phosphorylation status which leads to the al-

teration of substrate or ion transport, the ability to interact with regulatory proteins and

differential ability of inhibitors to block transporter uptake activity (Ozaki et al., Lesch

and Gutknecht, 2005).

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In various studies the relationship between several SNP polymorphisms within

the serotonin transporter gene and autism were studied with contradictory results (Kim

et al., 2002; Maestrini et al., 1999; Zhong et al., 1999; Persico et al., 2000, Conroy et

al., 2004).

A largely unexamined RFLP with two alleles in the 3’ untranslated region of the

serotonin transporter gene has also been identified (Gelernter and Freimer, 1994).

There was a new 381-bp DNA region identified in genomic clones located be-

tween the 5HTTLPR and the transcriptional start site. Study results suggest that this

sequence is deleted in approximately 50% of normal individuals, while other studies

found no deletion (Mortensen et al., 1999; Flattern and Blakely, 2000; Hahn and

Blakely, 2002).

There has been a number of SNPs described so far: there are at least 24 single

nucleotide polymorphism in the loci encoding the serotonin transporter (SLC6A4) and

at least 10 produce changes in the amino acid sequence (Hahn and Blakely, 2002).

3.2.3 The 5HTTLPR polymorphism

The most widely investigated polymorphism of the serotonin transporter gene

was identified by Heils et al., (1995, 1996), and named 5HTTLPR, referring to 5-HT

transporter length polymorphic region (Lesch et al., 1996) This polymorphism is located

1 kb upstream of the sequence encoding for the transporter protein, in the transcription

control region. As an insertion-deletion polymorphism, it consists of a series of repeats

within the promoter region, and the two most common alleles differ in length by 44

base pairs (Gelernter et al., 1998). Two common alleles were originally identified, the

long (l) and the short (s) allele. In case of the short allele, the 44 bp sequence is deleted,

while in case of the long allele it is inserted. The short allele consist of 14 repeat ele-

ments while the long allele 16 (Heils et al., 1995, 1996). 5HTTLPR influences the tran-

scription of the serotonin transporter gene, thus influencing the density and function of

the serotonin transporter (Heils et al., 1995, 1996). Basal activity of the l variant of the

serotonin transporter gene promoter is about twice as that of the short variant (Lesch et

al., 1996). In cells homozygous for the serotonin transporter gene protein expression

18

also differs, with cells carrying the ll genotype producing steady-state concentrations of

the serotonin transporter mRNA 1.4-1.7 times higher than cells carrying either the ss or

the sl genotype. Serotonin uptake in cells homozygous for the ll genotype was similarly

1.9-2.2 times as that in cells carrying the ss or sl genotype (Lesch et al., 1996). Several

studies with different targets, such as immortalized raphe cells (Mortensen et al., 1999),

post-mortem raphe mRNA concentration (Little et al. 1998), platelet serotonin uptake

and content (Greenberg et al., 2000), the responsivity of the serotonergic system to

clomipramine and fenfluramine challenge (Reist et al., 2001, Whale et al., 2000), mood

changes as a result of tryptophan depletion (Neumeister et al., 2002) and SPECT (Heinz

et al., 1999) support that the s allele of 5HTTLPR restricts the availability of the sero-

tonin transporter and ultimately the uptake of serotonin (Jacob et al., 2004). Because in

most studies ss and sl genotypes behaved similarly and they differed from the ll geno-

type equally, it was postulated that the 5HTTLPR polymorphism is of a dominant-

recessive nature (Lesch et al., 1996).

The 5HTTLPR polymorphism is present in simian but not in prosimian primates

and other mammals (Lesch and Mössner, 1998). The majority of alleles are composed

of 14 (short allele) or 16 (long allele) repeat units. Allele and genotype distributions of

5HTTLPR vary considerably across populations (Lesch and Gutknecht, 2005). Within

the Caucasian population, frequency of the s allele is 43% and frequency of the l allele

is 57% (Lesch et al., 1996). The distribution of the genotypes follows the Hardy-

Weinberg equilibrium: ll–32%, sl–49%, ss–19% (Lesch et al., 1996), although shows

variation in different ethnic populations (Gelernter et al., 1997). The structure of

5HTTLPR is the basis of the formation of such a DNA secondary structure that has the

potential to regulate the transcriptional activity of the serotonin transporter gene pro-

moter (Lesch and Gutknecht, 2005).

In addition to the two most common alleles (s with 14 repeats and l with 16 re-

peats) originally described, there are also rare 15, 19, 20 and 22 repeat alleles, many

often limited to a particular ethnic ancestry (Delbruck et al., 1997; Gelernter et al.,

1997; Kunugi et al., 1997; Michaelovsky et al., 1999), as well as novel alleles differing

in sequence composition (Nakamura et al., 2000).

From the time of its discovery there were attempts to associate the 5HTTLPR

polymorphism with personality traits originating from the observation that drugs target-

19

ing the serotonin transporter are effective mainly in depressive and anxiety disorders.

Lesch has found a significant association between the 5HTTLPR genotype and neuroti-

cism, with subjects carrying the s allele scoring higher on the neuroticism scale than

subjects not carrying the s allele (Lesch et al., 1996). Scores on scales measuring the

other major personality traits were unrelated to the 5HTTLPR genotype suggesting that

the effect of 5HTTLPR on personality was specific for neuroticism and neuroticism-

related traits (Lesch et al., 1996). These results has since then been replicated in other

studies while some studies found no such relationship (Hahn and Blakely, 2002; Willis-

Owen et al., 2004, Flory et al., 2005). In a metaanalysis of 26 studies, however, an asso-

ciation was found between the s allele and increased neuroticism (Sen et al., 2004a, b).

Results of studies in the past ten years suggest that 5HTTLPR may be associated

with personality traits related to anxiety, depression, and responsivity to stress (Lesch

and Gutknecht, 2005). There is also evidence suggesting that 5HTTLPR influences pre-

frontal cortex and amygdala activity. In tasks involving cognitive response control, peo-

ple carrying one or two copies of the s allele show higher prefrontal brain activity indi-

cating that the s allele is linked to enhanced prefrontal cortical responsiveness particu-

larly in the anterior cingulate cortex suggesting a strong relationship between cognitive

function and 5HTTLPR. It has also been reported that people carrying the s allele show

increased amygdala responsivity in response to fearful stimuli (Hariri et al., 2002).

These results support that genetic variation of serotonergic function contributes to the

response of brain regions underlying human emotional behaviour (Lesch and

Gutknecht, 2005).

There were efforts to find an association between the 5HTTLPR genotype and

psychiatric disorders. 5HTTLPR was associated with bipolar disorder in some but not

all studies and there are studies supporting the association of the s allele with unipolar

major depression (Furlong et al., 1998; Collier et al., 1996; Gutierrez et al., 1998; Hahn

and Blakely, 2002). In one study it was found that the l allele was associated with DSM-

IV melancholic depression and the s allele with atypical depression and from their find-

ings the authors concluded that the 5HTTLPR polymorphism is not the cause of affec-

tive disorders but rather influences the manifestation of the disease (Willeit et al., 2003).

In several studies the s allele was found to be significantly more frequent in major de-

pressive disorder than in controls (Hoefgen et al., 2005).

20

While studies yielded conflicting results on the association of the 5HTTLPR

genotype with psychiatric disorders, some studies tried to delineate the neuroanatomical

basis of the role of the 5HTTLPR polymorphism in susceptibility to depression.

Pezawas et al. (2005) reported that subjects with s allele have reduced grey matter vol-

ume of the perigenual anterior cingulate cortex (pACC) and of the amygdala. These two

regions are postulated to play a role in fear stimuli processing. The connectivity be-

tween these two areas is reduced in subjects carrying the s allele resulting in the uncou-

pling of this mood circuit as a result of the differential brain development of these re-

gions and possibly leading to altered emotional reactivity (Pezawas et al., 2005).

In newer studies an association between the 5HTTLPR and environmental fac-

tors has also been targeted. Caspi et al. (2003) found that the 5HTTLPR polymorphism

has a modulating effect on the role of stressful life events in the development of depres-

sion. Subjects carrying the s allele showed more depressive symptoms, depressive dis-

orders and suicidal behaviours in relation to stressful life events than subjects not carry-

ing the s allele, suggesting a gene x environment interaction. Grabe et al. (2005) found

similar evidence for gene x environment interaction.

Several other psychiatric disorders have been described to be associated with the

5HTTLPR polymorphism. Association with anxiety disorders was also described for the

5HTTLPR (Ohara et al., 1998). Alcohol dependence was also significantly associated

with the 5HTTLPR s allele in several studies (Herman et al., 2003; Munafo et al., 2005;

Feinn et al., 2005). The 5HTTLPR s allele was also associated with migraine with aura

(Juhász et al., 2003b, Marziniak et al., 2005).

An association of the s allele with seasonal affective disorder has also been re-

ported (Rosenthal et al., 1998). An association of both the s allele and the l allele of the

serotonin transporter genotype with suicide has also been reported, as well as no asso-

ciation with this polymorphism (Hahn and Blakely, 2002). Several studies have found

an association between the s allele of the 5HTTLPR and alcoholism. Data from several

studies suggest that there is a relationship between the s allele and impulsive violent

behaviour (Hahn and Blakely, 2002).

The role of the serotonin transporter in neurodevelopment has also gained much

attention recently. There is mounting evidence indicating that the homeostasis of the

serotonergic system is crucial in the genesis, differentiation and maturation of neurons

21

and neural networks in brain areas responsible for controlling sensory input, stimulus

processing and motor output (Lesch and Gutknecht, 2005). Serotonin plays an important

modulating role as a mitogenetic and morphogenetic factor and a differentiation signal

in cortical development (Gaspar et al., 2003). The role of serotonin as a differentiation

signal in brain development has been supported by morphological studies indicating the

role of serotonin in the formation and plasticity of both neocortical and subcortical

structures (Lesch and Gutknecht, 2005). Studies in knockout rodents show that inactiva-

tion of the serotonin transporter gene deeply disturbs the formation of the somatosen-

sory cortex. In heterozygous knockout mice (mutant mice lacking one 5HTT allele, 5-

HTT+/-) where the serotonin transporter availability is reduced leading to a smaller de-

lay in serotonin reuptake, distinctive irregularities in brain development can be ob-

served. The extent of reduction of transporter availability in these mice is similar to that

in humans carrying the s allele suggesting that the allelic variation of serotonin trans-

porter function might also affect the development of the human brain and thus might

play a role in a disposition both towards certain illnesses and to therapeutic response

(Lesch and Gutknecht, 2005).

It should also be taken into consideration, however, that not individual genes

alone, but gene x gene and gene x environment interactions play a role in brain devel-

opment, in neuroplasticity as well as in therapeutic response. An experiment with rhesus

macaques, nonhuman primates carrying rh5HTTLPR, where the interaction effect of the

rh5HTTLPR genotype and rearing conditions was investigated, showed that the concen-

tration of cerebrospinal 5HIAA was influenced by the rh5HTTLPR genotype only in

case of peer-reared monkeys, but not in the mother-reared group. In case of peer-reared

monkeys carrying the s allele, significantly lower cerebrospinal 5HIAA concentrations

were observed, indicating lower serotonin turnover which corresponds to studies sup-

porting that the s allele of the 5HTTLPR is associated with reduced binding and tran-

scriptional efficiency of the serotonin transporter gene (Lesch and Gutknecht, 2005).

Other studies with similar results have also been published supporting the role of both

genetic background and environmental factors as well as their interaction in neural and

behavioural development in nonhuman primates. It seems that environmental factors

might compound a specific vulnerability due to a genetic factor and also influence the

therapeutic response associated with a given genotype (Lesch and Gutknecht, 2005). In

22

a study investigating infant macaques, an association has been found between

rh5HTTLPR and the limbic-hypothalamic-pituitary-adrenal axis response to stress, and

this effect was modulated by early experience (Barr et al., 2004). This is very important

because chronic stress increases the risk for developing psychiatric disorders such as

depression, and dysregulation of the LHPA axis is commonly found in depressives

(Barr et al., 2004). The results of studies suggest that the contribution of genes on be-

haviour, personality and temperament is dependent on the interaction between genes

and the environment and this interaction leads to the expression of the results of envi-

ronmental factors only if the permissive genetic background is present (Lesch and

Gutknecht, 2005). The same result has been reached in the Caspi study (2003) where

people carrying the s allele had a two times greater chance of developing depression

after stressful life events, and adverse childhood experiences had an increased risk of

leading to depression in people carrying the s allele (Caspi et al, 2003).

Besides gene x environment interactions, gene x gene interactions (epistasis)

have also been described in case of the 5HTTLPR polymorphism. An interaction be-

tween 5HTTLPR and DRD4nR was observed on the Orientation score in 2-week old

newborns (Reif and Lesch, 2003). An association between 5HTTLPR and DRD4 has

also been observed in adults, with subjects with the sl genotype showing an increased

effect of the DRD4 genotype on the TCI novelty seeking score (Reif and Lesch, 2003).

An interaction between 5HTTLPR and a polymorphism in the gene encoding for

COMT has also been identified influencing the scores on the TCI Persistence scale. In

case of subjects homozygous for this COMT gene (carrying the met/met or val/val

genotypes), Persistence score was significantly elevated if the subject was also carrying

the 5HTTLPR s allele (Reif and Lesch, 2003).

23

3.2.4 Pharmacogenetics of the serotonin transporter gene

Until recently differences in drug response have been attributed mainly to dif-

ferences in pharmacokinetic processes but recent study results showed that pharma-

cologic drug response in a great part depends on the structure and functional expression

of a large number of gene products which are both pharmacokinetic and pharmacody-

namic determinants. There is considerable evidence supporting that response to antide-

pressants, anxiolytics and antipsychotic drugs is influenced by complex and polygenic

genetic factors besides environmental factors. While single genes have small effects on

drug response, the interaction of genes, however, can have dramatic effects. The sero-

tonin transporter is regarded as the initial site of action of several antidepressants, there-

fore it can be expected that polymorphism within this gene might also affect therapeutic

response to antidepressant drugs (Lesch and Gutknecht, 2005).

It has been described in several studies that allelic variation of the serotonin

transporter function does not only result in increased susceptibility to anxious and de-

pressive features but also to less favourable antidepressant response (Lesch and

Gutknecht, 2005). Smeraldi (Smeraldi et al., 1998) has found that patients carrying the

ss genotype showed poorer response to fluvoxamine than patients with ll and sl geno-

types. Zanardi (Zanardi et al., 2000) has found the same for paroxetine, while Pollock et

al. (2000) has found that response to paroxetine is faster in ll genotype patients. Murphy

et al. (2004) also concluded that the s allele is associated in general with a poorer re-

sponse to SSRI treatment. These results, however, are applicable mainly in European

populations (Lesch and Gutknecht, 2005), whereas in Korean and Japanese patient sam-

ples ss genotype patients exhibit a better response to fluoxetine, paroxetine and fluvox-

amine (Lesch and Gutknecht, 2005). There are many possible explanations for this phe-

nomenon. While the frequency of the l allele is 54% in the Caucasian population, it is

25-26% in Japanese and Korean populations (Lesch and Gutknecht, 2005), but ethnic

and environmental factors also might play a role.

The 5HTTLPR has also been implicated to be associated with lithium therapy

efficacy with contradicting results (Michelon et al., 2006). Association with the

5HTTLPR genotype has also been suspected in case of antidepressant induced mania in

bipolar patients and in rapid cycling (Lesch and Gutknecht, 2005).

24

3.3 Temperament

Temperaments are constant constellations of one’s personality, traits and ways

of reacting which characterise that person and remain constant during time and through-

out several diverse situations (Carver and Scheier, 1995). Most theories of temperament

contain three essential components: (1) that temperaments are related to emotionality,

(2) that temperaments are genetically determined and inherited and (3) that tempera-

ments are manifested from early childhood and remain relatively constant over life.

Temperaments are an important component of personality, along with character

and psyche (Svrakic and Cloninger, 2005). Temperaments involve basic emotions, de-

termining the way the organism is biased in the modulation of conditioned behavioural

responses to stimuli. In the beginnings of research into temperaments, Thomas and

Chess differentiated temperaments from motivation in that temperaments define the

stylistic component of behaviour as opposed to the content. In more modern theories of

temperament the emotional, motivational and adaptive aspects are also considered, and

the term temperament is more used to refer to the emotional reactivity and emotional

nature of personality (Carver and Scheier, 1995).

3.3.1 Earlier models of temperament

Allport defined temperament as the characteristic phenomena of an individual’s

emotional nature, his susceptibility to emotional stimulation, the strength and speed of

response, the nature of the prevailing moods, as well as all the characteristics of fluctua-

tion and intensity of mood, which are all viewed as dependent on constitutional makeup

and heritable (Watson et al., 2005).

Buss and Plomin postulated that there are several different temperaments, and

what differentiates them from the other personality traits is that they are genetically de-

termined (Carver and Scheier, 1995). They have defined temperaments as the inherited

personality traits which are obvious already in early childhood. Temperaments, how-

ever, influence not only childhood, but adult personality as well and thus their effect is

obvious throughout the whole life. In the model of Buss and Plomin there are three

25

types of personality dispositions that can be considered temperaments: activity level,

sociability and emotionality. In their model, emotionality predisposes to the increase of

physical activity in emotionally involving situations. Their concept of emotionality is

similar from several aspects to Eysenck’s neuroticism and emotional lability (Carver

and Scheier, 1995). Emotionality is defined as emotional reactivity to stress and it con-

tributes broadly to anxiety and depression (Eley and Plomin, 1997). There seems to be

substantial genetic influence on emotionality which can be concluded from quantitative

genetic research in both animals and humans and from twin and adoption studies in hu-

mans (Eley and Plomin, 1997).

3.3.2 Cloninger’s model of temperament

In his biological model of personality, Cloninger has identified four major tem-

peramental traits: harm avoidance, novelty seeking, reward dependence and persistence,

which the authors consider the modern interpretation of the four ancient temperaments:

melancholic is related to harm avoidance, choleric to novelty seeking, sanguine to re-

ward dependence while phlegmatic to persistence (Svrakic and Cloninger, 2005). As

compared to older models of temperaments, Cloninger’s conceptualizes his four tem-

peraments as genetically independent dimensions that occur not as exclusive categories,

but occurring in all combinations. These temperamental traits are therefore seen as heri-

table differences underlying the person’s automatic responses to danger, novelty, differ-

ent types of reward, and are closely associated with the four basic emotions: fear (harm

avoidance), anger (novelty seeking), attachment (reward dependence) and ambition

(persistence) (Svrakic and Cloninger, 2005). In this modern concept, temperament is a

heritable bias in emotionality and learning that underlies the acquisition of emotion-

based, automatic behavioural traits and habits that are observable already from early life

and remain relatively stable over life. According to observations, temperamental traits

tend to stabilize during the 2nd-3rd year of life. The basic temperamental dimensions are

normally distributed quantitative traits, and are moderately heritable. The temperaments

can be considered as spectrums, along which people are normally distributed. None of

the extremes of the individual spectrums has specific advantages and disadvantages, so

26

neither high, nor low scores on the scales measuring the individual temperaments mean

better adaptation. Cloninger’s four dimensions have been shown to be genetically ho-

mogenous and independently inherited. These temperamental traits have been sown to

be universal across several cultures (Svrakic and Cloninger, 2005).

In its classic definition, temperament refers to both the biological core of per-

sonality and its extreme and pathological expressions into personality disorders. Clon-

inger’s model postulates that the interaction of heritable traits influences personality

development by influencing life experiences, information processing, mood reactions

and adaptation in general (Maremmani et al., 2005). Based on the interaction of the

three core dimensions people develop particular patterns of behaviour. Cloninger also

suggested that when the extremes of the dimensions are combined, the resulting person-

ality corresponds to traditional personality disorders (Maremmani et al., 2005).

3.3.3 Akiskal’s model of affective temperaments

In Akiskal’s model, affective temperaments are subaffective trait expressions of

the subclinical phenotypes of affective disorders.

Temperaments have long been thought to be associated with mental illness. In

ancient Greek medicine, the harmony and balance of the four bodily humours was con-

sidered the basis of health. However, if the humours were out of balance specific disor-

ders would arise. Excess of the sanguine humour blood (which within the boundary of

health makes people active, amiable) could lead to mania, melancholic temperament

means proneness to depression, lethargy, contemplation. Choleric temperament is the

basis of irritability, hostility, bad temper, which in modern pathology might be related

to borderline personality disorder, while phlegmatic temperament, associated with indo-

lence, irresolution and timidity could be related to contemporary avoidant or schizoid

personality disorder (Akiskal, 2005). Akiskal has described five basic distinguishable

types of affective temperaments. The anxious temperament is characterised by exces-

sive worrying, while the depressive temperament means proneness to melancholy and

low mood. Subjects with hyperthymic temperament have a tendency for cheerful mood,

the cyclothymic temperament involves mood swings between high and low moods,

27

while the irritable temperament is characterised by scepticism and criticism as well as

anger and violence proneness. As they are temperaments, they have an early onset, per-

sist throughout life and are observable and characteristic of the person in all of various

life situations (Akiskal, 2005).

Akiskal derived his model of temperament based on clinical observations of af-

fective disorders developing on the basis of different predispositions. He identified dif-

ferent mood patterns in his clinical practice. Affective temperaments as described by

Akiskal and Mallya are derived from observations of clinical patients and relatives and

aim at the operationalisation of observable differences in these patients (Maremmani et

al., 2005). Affective temperaments are defined by the characteristic basal “affective

oscillations” (Akiskal, 2005). These oscillations in normal cases are minor and in ac-

cordance with daily events and cause no dysfunction, however, in some cases this alter-

nation is relatively bigger without obvious inner or external environmental causes. The

main affective temperamental types were described as hyperthymic, depressive, cyclo-

thymic, irritable and anxious. Akiskal’s model not only describes mood and affective

style but also risk for mood disorders in case of people with extreme temperaments

(Lara et al., 2006). Temperaments in this model are considered important mediators

between normal and pathological moods. Affective temperaments are such minor varia-

tions in the levels of affect and affective reactivity that is characteristic of a person.

Akiskal’s model captures basic affective style and mood patterns and identifies indi-

viduals carrying an increased risk for mood disorders. Affective temperaments are more

prevalent in relatives of mood disorder patients (Chiaroni et al., 2005; Lara et al., 2006).

Affective temperaments are associated with various traits and are hypothesised

to serve both social and evolutionary functions. Normal temperaments thus have their

ethological value, extreme temperaments, however, carry the danger of the development

of pathology.

There are important similarities and differences between the Cloninger and

Akiskal models of temperament. In Cloninger’s model, each temperament was identi-

fied as a pure and independently inherited trait which corresponds to basic emotions.

Akiskal on the other hand has developed his model of affective temperaments on the

concept of predisposition towards illness and the model was elaborated by observations

of mood patterns in clinical practice (Lara et al., 2006). The results of a study compar-

28

ing the Akiskal and Cloninger model in the general population showed that hyperthymic

temperament is correlated positively with novelty seeking and negatively with harm

avoidance; depressive temperament correlated positively with harm avoidance and

negatively with novelty seeking; and cyclothymic temperament correlated positively

with both harm avoidance and novelty seeking. Reward dependence and persistence was

uncorrelated with any of the affective temperaments. (Maremmani et al, 2005). From

the other aspect, subjects with dominant cyclothymic and hyperthymic temperaments

score higher on the novelty seeking scale than subjects with dominant depressive tem-

perament. Subjects with dominant depressive and cyclothymic temperament score

higher on the harm avoidance scale than groups with dominant irritable and hyper-

thymic temperaments. The irritable temperament does not correlate significantly with

any TPQ dimension (Maremmani et al., 2005)

Affective temperaments are subaffective trait dimensions representing the earli-

est subclinical phenotypes of affective disorders and persist as the subthreshold interepi-

sodic phase of these disorders (Maremmani et al., 2005). The identification of these

affective temperaments has important implications for the classification of mood disor-

ders as well as for their prevention, treatment and prognosis (Maremmani et al., 2005).

From this point of view, depression arises from the depressive temperament whereas

mania from hyperthymic temperament. Furthermore, if a temperament with opposite

polarity to the polarity of an affective period intrudes it gives rise to dysphoric or mixed

mania (Maremmani et al., 2005). Unstable cyclothymic temperament carries the risk of

depression switching into bipolar II disorder (Maremmani et al., 2005). Affective tem-

perament is associated not only with psychiatric illnesses but also with personality dis-

orders, such as borderline, narcissistic, histrionic, avoidant and dependent (Maremmani

et al., 2005). Borderline personality disorder in this model is related to cyclothymic

temperament, dependent or avoidant personality disorder to depressive temperaments

and associations have been described between narcissistic, histrionic and antisocial per-

sonality and hyperthymic and cyclothymic temperaments (Maremmani et al., 2005).

29

3.4 Neuroticism

Neuroticism (in other models also referred to as emotional stability-lability) is

considered a basic personality trait both by the classical Eysenck three-factor model and

the more modern five-factor personality models. Personality traits are prominent aspects

of personality exhibited in a wide range of important social and personal contexts

(APA, 1994). Thus traits are relatively stable characteristics of an individual observable

throughout various situations which are responsible for both the uniqueness and the uni-

formity of a given person. The extent of how much these traits are biologically deter-

mined varies from theory to theory. Thus, in contemporary psychology traits overlap

with temperaments to a great extent. Neuroticism was originally conceived as a person-

ality trait but some authors consider it a temperament because it fulfils the criteria (de-

termining emotional reactivity, early manifestation, stability over time and possible ge-

netic inheritance). The main reason for outlining neuroticism in more detail here is that

it is of special importance with regard to the 5HTTLPR polymorphism.

While in Eysenck’s model the neuroticism trait refers to emotional stability – in-

stability, in the subsequent five-factor models it is comprised of such dispositions as

anxiety, depression, hostility and impulsiveness (McCrae and Costa, 1996; Costa and

McCrae, 2005). Neuroticism is also related to harm avoidance in Cloninger’s model.

The neuroticism trait is also considered to play a great role in the background of psy-

chopathology, especially anxiety and affective disorders. People characterised by higher

neuroticism are more prone to experience negative affects like sadness, anger, shame as

well as having a poorer control over urges and impulses and show excessive concern

over their physical functioning (Costa and McCrae, 2005). In general, neuroticism is

conceived as a predisposition to experience psychological distress.

Eysenck in his research on the structure of personality described personality with

two uncorrelated, independent dimensions: extro-introversion and neuroticism. Neuroti-

cism was a dimension along which people with different extent of emotional stability

and lability can be lined up (Burger, 1986). Viewing the two dimensions simultane-

ously, people high on the neuroticism dimension might develop two major types of neu-

roses: hysterical (if extroverted) and dysthymic (if introverted) (Cartwright, 1974). In-

dependently of extro-introversion, people scoring high on the neuroticism scale have a

30

tendency to feel inferior, nervous and are sensitive and touchy, are highly suggestible

but not persistent. In more physical terms, they quiver when having to stand still, and

have a poor ability to adapt their vision to darkness (Cartwright, 1974). The two end-

points of the neuroticism dimension are stability and neuroticism. Already Eysenck has

proposed that neuroticism reflects emotionality and emotional reactivity.

People scoring high on the neuroticism scale tend to suffer more frequently from

a category of disorders referred to as neuroses. Already Eysenck postulated that neuroti-

cism, as a temperament, is genetically based, and he also tried to find biological corre-

lates of this psychological dimension. Eysenck tied neuroticism to the function of the

sympathetic nervous system. Neurotic people, who have a low activation threshold, ex-

perience negative affect even if exposed only to minor stressors – i.e., they are easily

upset. Emotionally stable people, who have a high activation threshold, experience

negative affect only when exposed to very major stressors – i.e., they are calm under

pressure. He postulated that people with sympathetic hyperactivity are more likely to

suffer from neurotic disorders. High scores on the neuroticism dimension indicate emo-

tional lability and overreactivity, emotional overresponsibility and these people experi-

ence difficulty in regaining their normal state after emotional experiences. Eysenck also

stated that although environmental factors also play a role, in a greater part these dimen-

sions are attributable to genetic factors (Burger, 1986)

Originally neuroticism was described based on large samples of mental patients

and was later extended to the normal population (Cartwright, 1974). In modern concept,

neuroticism characterised by dysphoria, anxiety, tension, emotional reactivity means a

general vulnerability, the higher the score on this dimension, the greater the chance of

developing neurosis. According to more recent research, neuroticism is 40-50% herita-

ble and is reasonably stable across adult life. About 55% of genetic risk for major de-

pression is shared by neuroticism (Kendler and Gardner, 1998) suggesting that there

may be common genetic factors predisposing to depression, neuroticism, and anxiety,

therefore several genetic studies incorporate depressive and anxiety symptoms into a

single phenotype.

31

3.4.1 Neurosis

As it has been mentioned above, people scoring high on the neuroticism scale

tend to suffer more frequently from a category of disorders referred to as neuroses. In

general, neurosis refers to a broad category of milder forms of mental disorders which

cannot directly be matched to organic causes. Neuroses are traditionally contrasted to

psychoses which are considered more severe and more debilitating mental disorders

also affecting the relationship to reality.

Although neurosis as a category of psychiatric disorders is not used in current

psychiatric classification systems, it is still a useful term to refer to a number of mental

states or conditions which are varied in their manifestation but are related to conditions

in which emotional distress and unconscious conflicts are manifested in different physi-

cal, psychological and mental disturbances. Contrary to the prevailing concept in con-

temporary psychiatric classification systems, which aim at using categories based on

one salient characteristic of a given psychiatric illness, neurosis grabs the abnormality

of the person as a whole, incorporating several co-occurring symptoms.

The expression was first used in 1769 by William Cullen. He derived neuroses

from the absence or excess of neural energy. Kraepelin, at the end of the 19th century

made a distinction between neurosis and psychoses (Kraepelin, 1921). As psychiatry

evolved, the concept of neurosis tightened as several diagnostic categories became in-

dependent and thus were removed from the neurosis category (Tringer, 1999).

Cullen included all illnesses of the nervous system related to perception or

movement, fainting or muscle spasms, but also epilepsy, hysteria or melancholia (Buda

et al., 1988). Cullen thus considered only disorders with organic causes as neuroses.

Pinel, however, broadened this view, maintaining that neurosis can be a functional or an

organic and functional illness (Buda et al., 1988). Classical forms of neuroses were de-

scribed at the end of the 19th and the beginning of the 20th century. Hysteria was de-

scribed by Briquet and Charcot, neurasthenia was coined by Beard in 1869, while psy-

chastenia was described by Janet in 1909.

In all of these subtypes the energy concept of neurosis was maintained, just as in

Freud’s neurosis concept, who derived neuroses from the struggle of unconscious psy-

chic forces, such drives against which the individual tries to fight to suppress them ac-

32

cordingly to the expectations of the society. If this struggle is unsuccessful, neurosis

results. Freud deprived neurosis of its organic, anatomic and physical bases by stating

that neuroses are caused by unconscious conflicts, and categorised them as real neuroses

(e.g. anxiety neurosis, post-traumatic neuroses, neurasthenia, hypochondria), psycho-

neuroses (e.g. conversion neurosis, obsessive neurosis), mixed neuroses and borderline

cases (Buda et al., 1988). Freud hypothesised that neurosis arises from inner conflicts

grounded in the first six years of life, and considered it attributable to the frustration of

sexual drives. Other psychoanalysts, such as Alfred Adler or H.S. Sullivan also empha-

sized the role of social determinants in personal adjustment, while Karen Horney high-

lighted childhood insecurity as playing a crucial role in the development of neurosis

(Buda et al., 1988).

In 1939 the American Psychiatric Association subdivided psychoneuroses as

hysteria (anxious and conversion neurosis), psychastenia (or obsessive states), hypo-

chondriasis, anxiety, neurasthenia, reactive depression and mixed psychoneuroses. In

1952, DSM-I under Psychoneurotic Disorders listed anxious, dissociative, conversion,

phobic, obsessive, depressive and psychoneurotic reactions. In 1968, DSM-II differenti-

ated between anxious, hysteric, phobic, obsessive, depressive, neurasthenic, depersonal-

isation, and hypochondriac neuroses, all carrying distinct symptoms based on which the

syndromatology of all neuroses could be distinguished (Buda et al., 1988). In the classi-

cal description, before 1980, the class of neuroses included anxiety disorders and other

mild mental disorders, as milder form of mood disorders as well (Lopez Pinero, 1983).

Neuroses thus have different subdivisions, different definitions, and there are

different theories about their ethiology, especially concerning the role of inherited and

environmental factors in their development. It is now the prevailing view that both ge-

netic and environmental factors have important roles. Even Freud has emphasised the

role of constitution and sensitivity to stress in the origins of neurosis. The familial ag-

gregation and the comparison of monozygotic and dizygotic twins also point to the im-

portance of inheritance. The influence of environmental factors, however, cannot be

neglected. In newer theories the importance of socialisation and learning processes were

also included in the neurosis concept. The rate of neurotics in different social strata

shows great differences, and in developed countries the rate of neuroses is much higher.

33

There are also gender differences, neurosis is about twice as common in women as in

men (Buda et al., 1988).

The neurosis category, however, was a broad and thus hardly solid or uniform,

which made it inconvenient for use in everyday medical diagnosis. The category lacks

straightforward and generally accepted diagnostic criteria and is conceived and ex-

plained differently by different experts. Also, the expression neurosis carries a negative

value. This led to a decrease in the use of neurosis as a psychiatric category, and one of

the more modern, tighter, more straightforwardly characterised diagnostic categories is

used instead, which, however, often fails to grab the given disorder in its wholeness.

Neurosis is not a diagnostic category either in ICD-10 or in DSM-IV, the two most

widely accepted classification systems nowadays used. Instead, neurosis was subdivided

into independent subcategories containing independent disorders with exact and distinct

diagnostic criteria. This led to the appearance of several patients whose symptoms did

not fit into any one of the single categories, also giving rise to the comorbidity expres-

sion. Not only can two or more disorders be present simultaneously, but also, these dis-

orders can be transformed into one another in time (Tringer, 1999).

What is common in all types of neuroses is suffering regardless of its exact na-

ture, intensity, and to some extent regardless also whether the person or his/her envi-

ronment suffers. Neurosis is also characterised by the lack of joy and enjoyment. While

contact with reality is maintained, neurosis is experienced as a self-alien state. In the

formation of neurosis, a special personality structure is crucial, with genetic and sociali-

sation factors playing an important role in the formation of that personality structure.

This state is nowadays referred to as cognitive vulnerability. Neurosis is characterised

by a special style of information processing, with negative preferences and imperativism

being typical. It is very common that conflicts are perceived as the cause of neurosis,

but these are rather the consequences of it. Neurosis is fluctuating and generally progre-

diates resulting in a pathological balance with the environment (Tringer, 1999).

Neurosis was traditionally considered a mental disorder which is not due to or-

ganic deviations in the central nervous system, there is no other organic process, and not

a psychotic mental disorder. In more modern concepts, neuroses are considered as part

of psychogenic disorders. Psychogenic disorders are either psychoreactive states with a

psychosocial origin, or neuroses with a socialisational origin. The frequency of psycho-

34

genic disorders in the population is estimated at 15-30% (Tringer, 1999). Neurosis in

this modern aspect is a category containing such disorders which, in the current popular

classification systems, are categorized as affective disorders, anxiety disorders, somato-

form disorders, dissociative disorders (Tringer, 1999).

In the background of neuroses biological characteristics of the central nervous

system, temperamental factors and the reactivity of the personality play a key role. The

social factors are rather conditions than causes, and social causal factors are more to be

found in the past than in the present. There is a great inherited part within neuroses, the

weakness of the central regulation of activity, which is considered as the physiological

basis of neuroses.

The biological basis of neurosis according to certain theories is the weakness or

imbalance of the central activity regulation which is genetically determined. As a con-

sequence of this, even in the normal environment the subject is often over- or underacti-

vated with his/her cognitive processes unable to restore the balance. This results in be-

haviours aimed at restoring the balance. If the activation is too high, stimulus avoidant

behaviour will emerge in order to avoid overactivation resulting in anxiety. This is

characteristic of anxiety and affective disorders. In contrast, people whose nervous sys-

tem is generally underactivated are characterised by stimulus seeking behaviour, charac-

teristic of hysterical conditions (Lopez Pinero, 1983).

Neurosis thus seems to be a broad concept with a solid biological and genetic

basis, which is less investigated today. Rather, the genetics of affective and anxiety dis-

orders are in the focus of attention, but the high comorbidity rate of these disorders, and

similarities in the results of the studies targeting the genetic background of these disor-

ders so far, for example the possible association of these disorders with the 5HTTLPR

polymorphism, raise the possibility that now distinct psychiatric disorders, which were

once all considered part of the neurosis group, may have a common genetic basis and

thus be genetically more closely linked than it has been thought in the past few years.

These results might argue for the justification of neurosis as a psychiatric category.

35

3.5 Depression

Depression is a cluster of symptoms with characteristic psychological, physical,

behavioural and vegetative features which differ in the extent of their manifestation.

The core symptoms of depression are loss of interest or pleasure (anhedonia) and de-

pressed mood. The term depression is used to denote a wide spectrum of moods and

mood disturbances from everyday low mood to diagnosed major affective disorder.

Disorders of mood have been known for thousands of years. The first written

account of depression dates back to ancient Egypt, where the Eber papyrus described an

illness characterised by severe hopelessness. In the Old Testament, Saul is described as

suffering from severe depression (Andreasen and Black, 1995). This illness was origi-

nally termed melancholia, a term which first appeared in the writings of Hippocrates in

the 4th century B.C., making mood disorders the oldest known psychiatric syndromes

(Andreasen and Black, 1995).

Depression is a well-known and frequently used expression in our everyday

lives. In general it is used to describe prolonged low mood, or a reaction to unpleasant

life events. Depression, as a medical term, however, refers to a state characterised by

severe depressed mood and the incapability to joy, the loss of previous interests as well

as several physical phenomena, which negatively influence both psychological and

physical wellbeing, causing severe distress as well as significant social, work and inter-

personal dysfunction (Andreasen and Black, 1995).

Depression is defined by different contemporary psychiatric classification sys-

tems in different terms, but in general, a given number of symptoms must be present for

a given period of time. Depression is part of a broader category of mental illnesses re-

ferred to as mood disorders. These illnesses are characterised by mood, vegetative and

psychomotor disturbances. In general, mood disorders include major depressive disor-

der, bipolar disorder, dysthymia, cyclothymia and subthreshold mood states (Akiskal,

2005).

Manifestation of mood disorder may vary in severity from the debilitating psy-

chotic depression to milder, often undiagnosed subthreshold and subclinical forms.

36

3.5.1 Subthreshold and subclinical forms of depression

A significant portion of the population suffers from low mood, and although be-

sides serious subjective suffering this causes severe work, interpersonal and marital dys-

function, their state is not diagnosed as depression because their symptoms do not reach

the diagnostic criteria. They either do not satisfy the criteria in the number of symptoms

or in the duration of symptoms, while the severity of the symptoms reaches the level

observable in diagnosed patients. Also, in many cases depression presents primarily

with physical symptoms, with very mild mood disturbances or altogether without any

major mood problems, in which case patients are never referred to psychiatry. These

patients are significant in their number, and based on several, long-term follow-up stud-

ies, these states are often intermedier states later leading to the development of major

depression. Several scientists and clinicians described subthreshold forms of depression

resulting in several syndromes each grabbing a different aspect of subthreshold depres-

sion.

Subclinical forms of depression have been described very long ago: Paskind in

1930 already noted minor affective symptoms recurring on a cyclical basis as well as

neurovegetative signs and symptoms such as anergia, headaches, insomnia, sexual dis-

turbances, gastrointestinal disturbances, palpitations, and anxiety symptoms (Akiskal et

al., 1997; Pezawas et al., 2003). Although most people suffering from subthreshold de-

pressive syndromes never seek medical help, patients presenting with depressive symp-

toms not meeting diagnostic criteria of any DSM-IV defined depressive disorders are

still fairly common outside psychiatric practices and the degree of impairment in some

of these cases is comparable to major psychiatric disorders, causing substantial dysfunc-

tion, work impairment and social disability (Rapaport and Judd, 1998; Angst and Meri-

kangas, 2001). Besides limitations in general role and work function, people suffering

from subthreshold depression report significantly increased health service use and need

for public assistance (Judd et al., 1997; Angst and Merikangas, 2001). The need for

treatment is also often comparable to that in case of major mood disorders (Maier et al.,

1997). Subthreshold depression is associated with significant psychological distress,

disability and poor health perception (Angst and Merikangas, 2001; Rucci et al., 2003)

and also leads to a significant decrease in psychosocial function (Judd et al., 1996; Judd,

37

1997; Angst and Merikangas, 2001). Subclinical depression patients also have a high

risk of developing major affective disorders in the future; more than 25% of subthresh-

old depression patients develop major depression in the next 2 years (Sherbourne et al.,

1994, Angst and Merikangas, 1997; Kendler and Gardner, 1998). Other studies indicate

that subsyndromal depression can be observed during the course of illness in case of

major depression patients where subsyndromal depressive symptoms may alternate over

time with major depressive and minor depressive symptoms (Judd et al., 1998). Sub-

syndromal depression shows a great similarity to major depression with respect to fam-

ily aggregation (Judd, 1997; Lewinsohn et al., 2003) and treatment response (Rapaport

and Judd, 1998) thus suggesting that less severe forms of depression are a part of a

broad spectrum of depressive disorders. In spite of the fact that major mood disorders

carry the highest risk of suicidal behaviour (Rihmer et al., 2002) one study has shown

that more suicide attempts are associated with subthreshold depression (25.8%) than

with major depression (11.1%), and subthreshold depressions cause similar impairments

as major depression such as increased use of medical and mental health services, greater

number of sick days, impairment in social and occupational functioning, and in addi-

tion, subclinical depressive symptoms are also more prevalent than major mood disor-

ders (Judd et al., 1997, Borrelli et al., 1999; Angst and Merikangas, 2001).

Depression is a heterogeneous phenomenon and current DSM-IV categories de-

fining different types of depressive disease fail to cover all forms of this disorder, leav-

ing a substantially large group of people suffering from subthreshold depressive symp-

toms without a proper medical diagnosis. Several categories have been proposed to

cover those people who complain of depression but do not meet the criteria for major

depression (Maier et al., 1997).

Dysthymic disorder is characterised by a reduced number of symptoms showing

a minimal duration of 2 years. Minor depression is defined by a shorter minimal episode

length and a smaller number of symptoms as major depression. However, subsyndromal

symptomatic depression is a less severe form of depression than dysthymic disorder and

minor depression. Recurrent brief depression (Angst and Hochstrasser, 1994; Maier et

al., 1997; Judd, 1997) is a disorder characterised by episodes occurring about once a

month for at least one year, meeting the symptomatic criteria for a mild to severe de-

pressive episode, but lasting for less than 14 days (usually 2-3 days). Recurrent brief

38

depression may occur spontaneously or can be triggered by mild psychosocial stress

(Pezawas et al., 2003). Masked depression patients present primarily with physical

symptoms and therefore this phenomenon can also be related to subsyndromal depres-

sive disorder without predominant mood disturbances (Rihmer et al., 1983; Maier,

1997).

Subsyndromal depressive disorder (Judd et al., 1994) is defined as the manifes-

tation of at least two symptoms usually associated with depression for at least two

weeks with or without depressed mood. The presence of only two symptoms causing

social dysfunction is enough to qualify for this category (Judd et al., 1994). Most com-

mon symptoms of subclinical depression include insomnia, feeling tired all the time,

recurring thoughts of death, trouble concentrating, significant weight gain, slowed

thinking and hypersomnia (Judd et al., 1994). One half of the patients (54.1%) reports

only two symptoms (Judd et al., 1994). It is fairly common in the population (one year

prevalence is 11.4%, Judd et al., 1994) and is associated with significant social and

work impairment. This condition has two subtypes. Subsyndromal depressive disorder

with mood disturbance has a one year prevalence of 3.4% (Judd et al., 1994). Subsyn-

dromal depressive disorder without mood disturbance has a remarkably high prevalence

in the population (one year prevalence is 8.4%, Judd et al., 1994) and it covers people

suffering from depression without associated mood disturbances, who thus never seek

the right professional help. Subsyndromal depressive disorder shows relationship with

masked depression in that its leading symptoms are primarily physical and vegetative:

insomnia, morning hypersomnia, fatigue, headache, abdominal pain, hyperventilation,

palpitation, erectile failure (Rihmer et al., 1983; Akiskal et al., 1997). This disorder is

also similar to atypical depression because its symptoms include weight gain (rather

than weight loss), hypersomnia (as well as insomnia) and slowed thinking (Judd et al.,

1994). Earlier studies conclude that this disorder is a dangerous, hidden problem in the

population because neither the patients nor the physicians discover that the symptoms

have to do with depression (Judd et al., 1994). This underlines the importance for estab-

lishing proper screening tools for the subclinical forms of depression and the need for

better understanding of the biological background of these subclinical forms of depres-

sion and their etiological and biological relationship to major mood disorders.

39

3.5.2 Neurobiological basis of depression

Mood disorder is probably the most frequent and prevalent form of mental ill-

ness (Nestler et al., 2002) and is almost twice as common in females as in males. De-

pression in current psychiatry is viewed as a heterogonous syndrome consisting of sev-

eral disorders with distinct causes and pathophysiologies (Nestler et al., 2002).

3.5.2.1 Neuroanatomy of depression

Depression involves complex central nervous system processes. Several brain

areas are implicated in the background of the diverse symptoms associated with depres-

sion.

We have very little knowledge about neural circuitry underlying normal and

abnormal mood (Nestler et al., 2002) but it is known that many brain regions play a role

in mediating the symptoms of depression. Brain imaging and autopsy studies have dem-

onstrated the role of several brain areas, including the prefrontal cortex, cingulate cor-

tex, hippocampus, striatum, amygdala and thalamus (Nestler et al., 2002). These areas

play different roles in the manifestation of depressive symptoms. The neocortex and the

hippocampus is responsible for the cognitive aspects of depression (memory impair-

ments, feeling of worthlessness, feeling of guilt, doom, suicidality), the striatum and

amygdala is responsible for mediating anhedonia, anxiety and reduced motivation. Hy-

pothalamus plays a role in the neurovegetative symptoms, such as changes in sleep,

appetite and energy and loss of sexual interest (Nestler et al., 2002).

The key changes observable in depression involve the disturbance of emotions.

There are four main areas in the brain which play an important role in the regulation of

emotions: the prefrontal cortex (PFC), the anterior cingulate cortex, the hippocampus

and the amygdala. The prefrontal cortex is responsible for behaviours related to reward

or punishment, it contains representations of goals and the behavioural responses

needed to reach those goals. The PFC is thus involved in both appetitive and avoidance

behaviours. The anterior cingulate cortex is implicated in the integration of attentional

and emotional inputs. The hippocampus plays a central role in learning and memory,

40

also involving emotional learning, while the amygdala is crucial in processing stimuli

with emotional significance as well as coordinating responses. Studies investigating the

role of these areas in depression have been expanding in recent years (Thase, 2005).

Areas related to information processing are also thought to play a role in the

neurobiology of depression. Characteristic cognitive alterations can be observed in case

of most depressed patients, such as interpretation of experiences from a negative per-

spective, and negative memory bias. Cognitive problems are also evident in more severe

cases of depression, such as poor concentration, compromised problem-solving skills

and decreased ability for abstract thinking. These neurocognitive changes involve the

prefrontal cortex, the hippocampus and other structures in the limbic system (Thase,

2005).

Nowadays the role of subcortical structures gains more attention (n. accumbens,

hypothalamus, amygdala) because of their contribution to such symptoms of depression

as motivation, sleep, appetite, energy, circadian rhythms and anhedonia (Nestler et al.,

2002).

Anhedonia, decreased interest and loss of mood reactivity is related to neural

circuits involved in anticipation and consummation of rewards involving the thalamus,

hypothalamus, nucleus accumbens and prefrontal cortex (Thase, 2005). Thus the im-

pairment of brain reward pathways is also thought to play a role in the background of

depression (Nestler 2002).

Psychomotor retardation, another characteristic symptom of depression, points

to the dysfunction of subcortical circuits connecting the thalamus, basal ganglia and

striatum (Thase, 2005).

The hypothalamus mediates various neuroendocrine and neurovegetative func-

tions (Nestler et al., 2002) It has been studied in relation to depression mainly because

of its role in the HPA axis. Other hypothalamic nuclei and neuropeptide transmitters

received less attention although they play a crucial role in mediating sleep, appetite,

circadian rhythm and sexual interest, which are among the main symptoms of depres-

sion.

The amygdala plays a role in fear and fear conditioning, and also in conditioned

responses for rewarding stimuli, and as a part of a larger circuit formed by the nucleus

41

accumbens, bed nucleus of stria terminalis and other regions it also plays a role in emo-

tional memory (Nestler et al., 2002).

Monoaminergic neurons (Locus coeruleus, raphe nuclei part of the ascending se-

rotonergic system) also play important roles in several symptoms associated with de-

pression (sleep, circadian rhythm, memory, cognitive functions, eating, etc), and in ad-

dition they modulate all above areas through their projections and receptors expressed in

these areas (Thase 2005).

3.5.2.2 Neurotransmitters

Several neurotransmitter systems play a role in the background of depression.

The cathecholamine and later the monoamine hypothesis was the first attempt to link

depression to specific biochemical disturbances in the brain. Although this hypothesis

has been substantially revised, noradrenalin and serotonin are still thought to play a cen-

tral role in the neurochemical background of depression. Decreased central noradrener-

gic activity has been observed in the brain of depressed patients, with a dissociation of

noradrenergic activity in certain brain areas and thus increased noradrenergic function

in the medial forebrain bundle (Thase, 2005).

Originally the catecholamine hypothesis linked depression to the low noradrena-

lin levels in the brain. Several antidepressants, such as imipramine, by inhibiting the

reuptake, increased noradrenalin levels in synapses, while MAO inhibitors increased

synaptic noradrenalin levels by inhibiting the enzyme responsible for noradrenalin deg-

radation. Reserpin, which depletes monoamines, leads to an increase in depressive

symptoms. Some studies showed that some depressed patients show decreased levels of

MHPG (3-methoxy-4-hydroxyphenylglycol), the main metabolite of noradrenalin (An-

dreasen and Black, 1995). Among other effects, tricyclic antidepressants inhibit

noradrenalin uptake, while some new antidepressants inhibit noradrenalin uptake selec-

tively. Others antidepressants have α2-antagonist properties.

Other neurotransmitters also play a role in depression. Serotonergic dysfunction

in depressed patients has also been revealed by research (Thase, 2005). Newer antide-

pressants act through the inhibition of the serotonin transporter, thus increasing synaptic

42

levels of serotonin. Patients with severe depression also show decreased levels of 5-

HIAA in the liquor, which is the main metabolite of serotonin (Andreasen and Black,

1995).

It has long been described that abnormal serotonergic function plays a role in

affective disorders since serotonin transporter binding is reduced in mood disorder pa-

tients, a result interpreted as a compensatory response to central serotonin deficiency

(Owens and Nemeroff, 1998). It has also been demonstrated in imaging and post-

mortem studies that depressed individuals have reduced serotonin transporter expression

in the brain (Lira et al., 2003).

Results from knock out mice studies also point to the role of serotonin in depres-

sion. Mice homozygous for the null mutation (5HTT-/-) exhibit reduction in dorsal ra-

phe firing as well as desensitization and downregulation of somatodendritic 5HT1A

autoreceptors. Postsynaptic 5HT1A receptors are also reduced in the frontal cortex,

amygdala, septum and hypothalamus (Holmes et al., 2003). The binding density of

5HT2A receptors is increased in the hypothalamus, while 5HT2C receptor density is in-

creased in the amygdala (Holmes et al., 2003). The impairment in dorsal raphe nucleus

function leads to reduced serotonergic function and might play a causative role in de-

pression (Lira et al., 2003). These results also have implications for the use of seroton-

ergic antidepressants during pregnancy, since inhibition of the serotonin transporter at

critical periods of development might increase vulnerability for affective and anxiety

disorders (Lira et al., 2003, Alexandre et al., 2006).

The acethylcholinergic system has also been implicated in the background of

depression. The increase of cholinergic activity decreases monoaminergic brain activity.

Cholinergic agonists increase depressive symptoms, like dysphoria and psychomotor

slowness (Andreasen and Black, 1995). Tricyclic antidepressants have anticholinergic

properties as well.

Several neurophysiological differences are observable in depression. Most stud-

ies focused on sleep EEG differences in depressed patients: decreased REM latency,

decreased slow-wave sleep, and increased REM density which coincides with insomnia,

a frequent symptom of depression (Andreasen and Black, 1995).

43

3.5.2.3 Neuroendocrine function

There are differences in neuroendocrine function observable in depression (An-

dreasen and Black, 1995). Metabolites of cortisol are increased in the urine of depressed

patients and there is an increased plasma cortisol level. Dexamethasone suppression

test, an indicator of the hypothalamus-hypophysis-adrenal gland system also shows

characteristic differences in case of depressed patients. Suppression of the normal corti-

sol response after dexamethasone provocation can be observed in depressed patients

(Andreasen and Black, 1995). The differences in the function of other neuroendocrine

systems indicate that the difference is at the level of hypothalamic regulation (An-

dreasen and Black, 1995).

Many modern hypotheses dealing with the neurobiology of depression investi-

gate the dysregulation of the HPA axis and hippocampus, and focus on CRF, glucocor-

ticoids, BDNF and cREB.

The hypothalamus-pituitary-adrenal axis is activated in response to acute stress

and as a result the level of glucocorticoids is increased which, among other effects, act

on different brain regions thus influencing behaviour (Nestler et al., 2002). Increased

levels of glucocorticoids under normal conditions inhibit HPA activity through their

action on the hippocampus, and also promote certain cognitive abilities. Excessive acti-

vation of the HPA axis can be observed in about half of depressed patients, some ex-

hibit increased cortisol production and decreased DST (dexamethasone suppression

test), and in some patients CRF is hypersecreted (Nestler et al., 2002). The role of the

HPA hyperactivity in depression is not fully understood, but current hypotheses suggest

that elevated glucocorticoid levels over sustained time periods might be toxic to hippo-

campal neurons, which might contribute to the cognitive impairment observable in de-

pressed patients. Due to this damage the inhibitory control of the hippocampus on the

HPA axis is decreased. Increased HPA activation might also contribute to depression

also by way of enhanced CRF transmission in the hypothalamus, since central admini-

stration of CRF causes symptoms similar to depression, such as increased arousal, de-

creased appetite and sexual behaviour and increased heart rate (Nestler et al., 2002).

Furthermore, chronically increased glucocorticoid concentration markedly alters func-

tions mediated by 5-HT receptors (Bagdy et al., 1989). It is still not known, however,

44

whether HPA abnormality is the cause of depression or is secondary to some common

cause.

It has been suggested that increased CRF function and increased activity of the

HPA axis observed in depression and anxiety disorders might be related to the dysfunc-

tion of serotonergic regulation. Agents increasing serotonin levels and selective 5HT1A,

5HT2A, 5HT2C agonists activate CRF secretion of hypothalamus (Bagdy et al.,1989;

Calogero et al., 198;, Van de Kar,1999), and the almost exclusive role of the hypotha-

lamic paraventricular nucleus in these responses has also been shown (Bagdy, 1996;

Bagdy and Makara, 1994, 1995).

3.5.2.4 Neurotrophic factors

The role of neurotrophic factors have also been implicated in the background of

depression. These factors not only regulate neuronal growth and differentiation during

development but in case of adult cells they are also regulators of activity and survival

(Nestler et al., 2002). It is postulated that deficiency in neurotrophic support may play a

role in hippocampal pathology and thus depression. Most of recent research focuses on

BDNF which is decreased by chronic and acute stress in a process mediated partly by

glucocorticoids and stress-induced changes in serotonergic neurotransmission in the

dentate gyrus and the hippocampus (Nestler et al., 2002). Antidepressants can increase

BDNF levels suggesting that antidepressant induced upregulation of BDNF might play

a role in repairing stress-induced hippocampal damage and also in protecting vulnerable

neurons (Nestler et al., 2002). In the action of BDNF cREB is involved (cAMP response

element binding protein). cREB induces the BDNF gene and cREB levels are increased

by all antidepressants in several brain regions including the hippocampus (Nestler et al.,

2002).

45

3.5.3 Genetic background of depression

It has long been observed that just as several other types of psychiatric disorders,

depression also tends to aggregate in families and tends to be inherited. The heritability

of mood disorders has also been supported by several studies. The focus of recent stud-

ies is the identification of specific genes which play a role in the background of depres-

sion. Genetic studies also reveal that there is substantial genetic similarity between bi-

polar and unipolar depression, although the biological and genetic background seems to

be stronger in bipolar depression (Kelsoe, 2005).

The familial, inherited nature of depression has been observed long ago, al-

though familial aggregation does not always infer a genetic definition, because role pat-

terns, learned behaviours, socioeconomic and cultural environment and physical factors

influencing the emergence of depression are also familial (Andreasen and Black, 1995).

Studies of familial aggregation, however, argue for a genetic basis of depression: the

frequency of depression (both unipolar and bipolar) was significantly higher among first

degree relatives of patients. Twin and adoption studies also support these results. Link-

age studies also point to the same direction (Kelsoe, 2005).

According to data from twin studies, genes are responsible in 50-70% of the

ethiology of mood disorders, while the remaining 30-50% is due to environmental fac-

tors, meaning that inheritance is responsible for a predisposition or increased risk. In

genetic studies a greater attention is paid to bipolar disorder than unipolar forms of de-

pression. Several genes or DNA sequences have been implicated as related to bipolar

disorder (4p16, 4q35, 6q, 8p, 10p12, 10q25, 12q23-24, 13q32, 16p13, 17q, 18p11,

18q21, 18q22-23, 21q22.3, 22q11-q12, Xq26-q28). In case of unipolar depression there

are fewer results available (Andreasen and Black, 1995).

The lifetime prevalence of unipolar major depressive disorder is at least 10%

and the heritability based on twin studies is between 40 and 50% (Levinson, 2006; Nes-

tler et al., 2002). The relative risk of first degree relatives of major depressive patients to

develop depression is 2-3 as compared to the general population (Levinson, 2006). The

mode of inheritance has not been delineated so far, and several environmental factors

such as childhood abuse and neglect and early life stress also play a role.

46

Genetic studies focusing on the background of depression might utilize several

approaches. Besides twin studies there are association studies of candidate genes and

linkage studies. Most candidate gene studies investigate the association of depression

with the 5HTTLPR polymorphism, and in several studies a significant association was

found in case of unipolar major depression (Hoefgen et al., 2005) and with bipolar de-

pression (Bellivier et al., 1998) as well. In other studies this gene was associated with

scales measuring neuroticism, such as a scale in NEO-PI-R or the harm avoidance scale

in Cloninger’s TCI (Levinson, 2006), a personality dimension thought to be associated

with an increased risk for developing depression. Other studies conclude that the role of

5HTTLPR in the background of depression is manifested only in interaction with the

effect of life events. Caspi (2003) reported that the relationship between stressful life

events and subsequent depression is predicted by the 5HTTLPR genotype. This may

suggest that 5HTTLPR plays a role in influencing stress reactivity, rather than depres-

sion itself (Levinson, 2006).

Another candidate gene is the TPH2, encoding the tryptophan hydroxylase 2 iso-

form which is the synthesizing enzyme of serotonin and is predominant in the brain.

This gene has also been found to be associated with major depression (Levinson, 2006).

A more recent hypothesis about depression is that excessive corticotropin activ-

ity leads to neurotoxicity which results in damage to hippocampal cells mediating many

depressive symptoms. Genetic factors influence the balance of neurotoxic and neuropro-

tective responses to stress. BDNF is one of the neuroprotective proteins and association

has been found between reduced levels of BDNF and depression, which has drawn at-

tention to polymorphisms affecting BDNF expression (Levinson, 2006).

3.6 Anxiety

Anxiety is a feeling of apprehension and fear also accompanied by physical

symptoms. Anxiety is a normal innate physiological and emotional alarm response to

the anticipation of danger or threat to the organism. It is an adaptive reaction accompa-

nied by increased somatic and autonomic activity preparing the organism for flight or

fight. Anxiety is thus crucial for the survival of an organism, but it can become abnor-

47

mal either when it is excessive or when it does not coincide with the threat in space or

time. When anxiety becomes pathological it results in strong subjective feelings and

physiological activation (including muscle tension, shortness of breath, hyperventila-

tion, palpitation, perspiration) (Charney et al.,1996; Andreasen and Black, 1995).

Unlike depression, anxiety has been described not so long ago. The first reports

of anxiety came from Da Costa who published his writing in the American Journal of

Medical Sciences in 1871 emphasising its cardiovascular symptoms (Da Costa, 1871).

Soon after this first description psychiatrists started to deal with the psychological as-

pects of anxiety. Freud has introduced anxiety neurosis emphasising the subjective feel-

ings involved, such as fear, panic, and feeling of doom. During this period, the relation-

ship between the somatic and psychological symptoms of anxiety was still debated. At

the beginning of the 20th century William James postulated that psychological experi-

ence accompanying anxiety is only the awareness of physical symptoms, while Freud

has thought that psychological symptoms lead to the development of the somatic symp-

toms of anxiety (Andreasen and Black, 1995). Research has since delineated several

psychiatric illnesses where excessive subjective anxiety is a leading symptom, accom-

panied by various other psychological and physical symptoms related to anxiety and

summarized them as anxiety disorders.

Jaspers has defined anxiety in opposition to fear as having no obvious object and

thus being more incomprehensible. Anxiety is an unpleasant emotional condition caus-

ing severe distress, characterised by feeling of worry, threat and terror. In the emergence

of anxiety the assessment and labelling of the situation is crucial, which is based on in-

herited characteristics, previous life events and the current state of the central nervous

system. Anxiety emerges in situations which are perceived uncontrollable and threaten-

ing at the same time (Carver and Scheier, 1995; Andreasen and Black, 1995).

3.6.1 Neurobiological basis of anxiety

Anxiety, although experienced as a distressing state, is an evolutionally and bio-

logically normal, adaptive condition. The role of anxiety is to increase the activation of

the central nervous system and organize behaviour in order to cope with an internal or

48

external threat most successfully. Anxiety becomes pathological when this reaction is

extreme or does not coincide in space or time with the threat. Anxiety is organized at

several levels of the central nervous system, with the amygdala playing an integrating

and coordinating role (Charney et al., 1996).

3.6.1.1 Neuroanatomy of anxiety

Visual and auditive sensory information reaches the cortex and the amygdala

through the thalamus, while olfactorial information goes directly to the amygdala and

the entorhinal cortex. Primary sensory receptive areas in the cortex project to unimodal

and polymodal cortical association areas, which in turn project to the amygdala, the

entorhinal cortex, the orbitofrontal cortex and the cingulate gyrus. All sensory informa-

tion is also projected to the hippocampus through the entorhinal cortex. After primary

processing in the sensory cortex, anxiety-related information is transferred to subcorti-

cal structures which play a greater role in the affective, behavioural, somatic and vege-

tative responses related to fear and anxiety. The amygdala plays a crucial role in the

transmission and interpretation of anxiety inducing sensory stimuli. Several neuro-

transmitters are implicated in the regulation of anxiety. The noradrenergic and seroton-

ergic systems, and several neuropeptides, such as CRF, opioids, CCK, NPY, and

galanine play a central role (Charney et al., 1996).

The amygdala plays a central role in the transmission and interpretation of sen-

sorial information leading to fear and anxiety, as well as integrating the neuroendocrine

components of response to stress. The amygdala receives afferentation from the sensory

and visceral systems of the thalamus, and it also receives exteroceptive sensorial infor-

mation from cortical areas and visceral sensory information from subcortical areas.

Dense and close associations with the orbitofrontal cortex give the basis for adaptive

behavioural responses which also incorporate the nature of the threat as well as earlier

experiences. Responses organized by the amygdala are executed via projections to the

vegetative, neuroendocrine and motor systems, with the periaqueductal grey matter, the

locus coeruleus, the hypothalamus and the striatum playing an important role (Drevets

and Charney, 2005).

49

The hypothalamus integrates information from various areas into a pattern of

coordinated sympathetic responses. The hypothalamus plays a role in mediating hormo-

nal and sympathetic responses to anxiety provoking information. While the lateral hy-

pothalamus is responsible for sympathetic activation (increase in blood pressure and

pulse rate, sweating, piloerection), the activation of the paraventricular nucleus leads to

the release of hormones and peptides important in the regulation of anxiety (Drevets and

Charney, 2005; Charney et al., 1996).

The activation of the locus coeruleus increases as a result of fear, anxiety or

stress, leading to sympathetic activation. The locus coeruleus innervates limbic and cor-

tical areas responsible for adaptive response to anxiety provoking stimuli. Through its

effect in the regulation of the noradrenergic neurotransmission the locus coeruleus plays

a central role in mediating anxiety (Drevets and Charney, 2005).

Cortical structures, such as the orbital and medial prefrontal cortex are important

in interpreting the significance of stimuli and modulating behaviour according the con-

tingencies of punishment and reward, these areas thus also play a role in evaluating

threatening information. Cortical areas are also important in predicting social conse-

quences of behavioural responses. Cortical areas have reciprocal associations with the

amygdala, and some areas also play a role in modulating periferial responses to stress

(Drevets and Charney, 2005).

Responses to anxiety provoking stimuli involve the neuroendocrine system (with

the paraventricular nucleus of the hypothalamus playing a coordinating role), the vege-

tative nervous system, and the motor system (Drevets and Charney, 2005).

3.6.1.2 Neurotransmitters mediating anxiety

Several neurotransmitter systems are responsible for mediating anxiety.

Anxiety provoking stimuli increase central noradrenergic neurotransmission in

the limbic system, the locus coeruleus and the cortex (Neumeister et al., 2005).

Dopamine release and metabolism is increased in response to acute, low-

intensity stress in several brain areas including the medial prefrontal cortex and the

amygdala. If the intensity or duration of stress increases, dopamine release is also in-

50

creased in the medial and nigrostriatal systems. Uncontrollable stress activates dopa-

mine release in the medial prefrontal cortex while inhibits dopamine release in the nu-

cleus accumbens (Neumeister et al., 2005).

Several neuropeptides, such as the opioids, the CCK, the NPY, galanine, AVP

and CRF also play a complex role in coordinating anxiety (Neumeister et al., 2005;

Charney et al., 1996).

The serotonergic system regulates anxiety in at least three distinct mechanisms

involving both anxiogenic and anxiolytic projections. Serotonergic projections involv-

ing 5HT2 receptors in the amygdala (from the dorsal raphe) and the hippocampus (from

the dorsal and medial raphe) mediate anxiogenic effects, while in the hippocampus

(from the medial raphe) involving 5HT1A receptors mediate anxiolytic effects

(Neumeister et al., 2005; Charney et al., 1996). Anxiogenic 5HT2 receptors have also

been found and identified as 5HT2C subtype (Bagdy, 1998; Bagdy et al., 2001).

Several studies have supported an association between serotonin transporter

function and anxiety (Jennings et al, 2006). It has been found that mice overexpressing

the serotonin transporter show decreased anxiety in several laboratory anxiety models,

whereas serotonin transporter knock out mice exhibit an increased anxiety phenotype

(Holmes et al., 2003; Lira et al., 2003, Lesch et al., 2003). These results support a causal

relationship between serotonin transporter function and anxiety related behaviours

(Jennings et al., 2006) Studies on the role of the serotonin transporter in anxiety regula-

tion thus yielded contradicting results, since they contradict behaviour observable as a

response to SSRI treatment. SSRIs decrease anxiety, although as an acute effect they

lead to increased anxiety (Bagdy et al., 2001; Millan, 2003). It has been described that

the elevated anxiety phenotype observable in serotonin transporter knock out mice

might be a consequence of missing serotonin reuptake in early age, leading to an altera-

tion in the development of cortical structures and distribution of serotonin receptors. It

has been demonstrated in experiments that in serotonin transporter knock out mice the

formation of the somatosensory cortex is disturbed. This suggests that allelic variation

of the serotonin transporter function might also influence the development of the human

brain, which might result in an increased susceptibility for anxiety and affective disor-

ders (Lesch et al., 2003). Besides the serotonin transporter, the 5HT1B receptors also

play a key role in this process (Lesch et al., 2003). Increased extracellular serotonin

51

concentration also interferes with apoptotic processes during neurodevelopment. Thus

changes in the function of the serotonergic system due to the inactivation of the sero-

tonin transporter in 5HTT knock out mice exert a long-term effect on cortical develop-

ment and adult brain plasticity, which might play a role in the neurodevelopment of

processes underlying negative emotionality, aggression and violence (Lesch et al.,

2003).

It has also been demonstrated that in 5HTT knock out mice and also after

chronic administration of SSRIs a desensitisation of 5HT1A receptors occurs, and results

indicate that 5HT1A receptors may play a role in the effects of 5HTT on emotion (Li et

al., 2000). It has also been shown that the reduction of the 5HT1A receptor density in

5HTT knock out mice follows a region-specific pattern in the brain and is more exten-

sive in female mice (Li et al., 2000). The most marked reduction in the density of

5HT1A receptors can be observed in the dorsal raphe nucleus, and is also observable in

the median raphe, most hypothalamic nuclei, and some nuclei of the amygdala and sep-

tum (Li et al., 2000). From other studies it is also obvious that the density of 5HT2A and

5HT2C receptors, similarly playing a role in mood regulation, is also altered in 5HTT

knock out mice in a region-specific manner (Li et al., 2003). 5HT2A receptors are in-

creased in the hypothalamus and septum and are decreased in the striatum, while 5HT2C

receptor density is increased in the amygdala, and all three of the above structures are

part of the limbic system related to emotional regulation (Li et al., 2003). The changes

in the density of 5HT2A and 5HT2C receptors thus probably play a role in increased

anxiety and emotional changes observable in 5HTT knock out mice (Li et al., 2003).

3.6.2 Genetic background of anxiety

Twin and family studies support that anxiety has a genetic background (Meri-

kangas, 2005; McMahon and Kassem, 2005). Morbidity in case of first degree relatives

of panic disorders patients is 8% compared to 2% in the general population (Andreasen

and Black, 1995). Concordance in case of monozygotic twins is 45% for panic disorder,

and 15% for dizygotic twins. Studies indicate that over 30% of total variability for anxi-

ety-related traits seems to be explained by genetic factors (Clement et al., 2002). Several

52

putative genes emerged as possible candidates, involved in the pathophysiology of

anxiety disorders, including genes involved in GABAergic and serotonergic neuro-

transmission but studies failed to find an association between genes encoding GABAer-

gic and serotonergic receptors and anxiety (Clement et al., 2002). More recently re-

search has started to focus on genes encoding elements of adrenergic (Clement et al.,

2002), dopaminergic (Henderson et al., 2000), adenosinergic (Deckert et al., 1998) and

cholecystokinergic (Wang et al., 1998) transmission as well (Clement et al., 2002). The

5HTTLPR (Gelernter et al., 1998; Lesch et al., 1996) and the 3’ VNTR polymorphism

in the serotonin transporter gene (Ohara et al., 1999) has also been implicated. In ge-

netic mapping and linkage studies using animals several loci have been reported to be

associated with anxiety related behaviours (Clement et al., 2002)

4. OBJECTIVES

The aim of our studies was to outline the role of the s allele of the 5HTTLPR

polymorphism of the serotonin transporter gene in the background of subclinical de-

pression, affective temperaments and anxiety traits in a psychiatrically healthy popula-

tion. The tendency for emotionality, increased anxiety and lower mood has been con-

ceptualised in the neuroticism personality trait and in earlier studies the association of

the s allele with neuroticism has been confirmed. Since neuroticism this way is a com-

plex phenomenon, it was not possible to determine whether its different aspects, emo-

tional reactivity, anxiety and depressiveness and their subtypes and symptoms are

equally responsible for this genetic association, or only one or a few of them is mark-

edly related to this polymorphism. The aim of our studies thus was to investigate the

relationship of these aspects of neuroticism and the s allele independently. The main

objectives in our studies were:

1. Is subthreshold depression, as indicated by elevated Zung Self-rating Depression

Scale scores related to the s allele in a psychiatrically healthy sample?

2. Is the relationship between the s allele and subclinical depression valid if we

consider only physical and vegetative symptoms of depression?

53

3. Are the psychological and physical-vegetative symptoms equally or differen-

tially associated with the s allele?

4. Is there any relationship between the s allele and increased anxiety in a psychiat-

rically healthy population?

5. Is the s allele also related to affective temperaments in the general population? It

is accepted that extreme affective temperaments can be considered the subsyn-

dromal manifestations of affective disorders, and affective disorders are likely to

be associated with the s allele.

6. Is there any difference in the 5HTTLPR / anxiety relationship between mi-

graineurs and non-migraineurs in a psychiatrically healthy sample?

5. METHODS

5.1 Subjects and measures

5.1.1 General aspects

All subjects in our study were unrelated, female and of Caucasian origin, the age

of the participants was 18-64 years. All subjects went through thorough neurological

and psychiatric screening. Subjects with any current or lifetime Axis I disorders accord-

ing to the DSM IV (American Psychiatric Association, 1994) criteria were excluded.

The study protocol was approved by the local ethics committee for experimentation on

humans and every subject gave informed consent before participating in the study.

Each subject was genotyped for the 5HTTLPR polymorphism of the serotonin

transporter gene.

In case of all subjects DNA was collected by buccal swabs. In case of each sub-

ject the inner side of the oral cavity was dabbed with a sterile swab in order to collect

buccal cells. Afterwards the swabs were left to dry for 24 hours before storing. The

swabs were then stored in their protective covering until further processing.

54

5.1.2 Investigation of the association between the 5HTTLPR s allele and

subthreshold depression

128 healthy Caucasian female subjects participated in the study. The mean age

was 38.49 years (±1.2476). All subjects were genotyped and completed the standardised

Hungarian version of the Zung Self-rating Depression Scale (Zung, 1965; Simon,

1998).

The primary reason for choosing the Zung Self-rating Depression Scale (ZSDS)

was that it contains more items related to the vegetative and physical aspects of depres-

sion than other self-rating depression scales. By the consensus of our group of research-

ers, we have identified a Physical-vegetative Symptoms Subscale within the ZSDS con-

sisting of 8 items:

2. Morning is when I feel the best

4. I have trouble sleeping through the night

5. I eat as much as I used to do

6. I still enjoy sex

7. I notice that I am losing weight

8. I have trouble with constipation

9. My heart beats faster than usual

10. I get tired for no reason

The subjects completed the original 20-item Zung Self-rating Depression Scale.

The groups carrying different genotypes were compared with respect to their total score

on the ZSDS as well as their score on the Physical-vegetative Symptoms Subscale and a

subscale containing the remaining 12 items of the original scale.


anxiety

101 Caucasian female subjects entered the study, 47 of whom suffered from mi-

graine without aura. Migraine without aura patients were referred from the Headache

55

Clinics of the National Institute for Psychiatry and Neurology and Sport Hospital, Bu-

dapest, Hungary. The other 54 subjects were staff members and university students who

had only rare (less than 1/month) and mild, if any, headaches. Family history of mi-

graine in non-migraineurs has been excluded by personal interview. A detailed medical

history was taken from each subject and all subjects were screened for other neurologi-

cal and psychiatric disorders on two occasions: at the beginning of the study and six

months later. Subjects with any other neurological and current and lifetime Axis I psy-

chiatric disorders according to the DSM-IV (American Psychiatric Association, 1994)

criteria were excluded. Of the 47 migraineurs who entered, 45 completed the study

(mean age: 41.73±1.41); one refused the genetic test, and one patient was excluded be-

cause of current episodes of minor depression meeting DSM-IV criteria. Of the 54

healthy non-migraineurs who entered, 52 completed the study (mean age: 42.0±1.70),

and two was found to have current minor depression according to DSM-IV criteria. All

subjects completed the standardised Hungarian version of Spielberger’s State Trait

Anxiety Inventory (STAI) (Spielberger, 1970; Sipos et al., 1998).


affective temperaments

139 unrelated females of Caucasian origin participated in the study. The mean

age was 31.39±1.0279 years. All subjects completed the standardized Hungarian ver-

sion of the original, 110-item TEMPS-A questionnaire (Akiskal and Akiskal, 2005a;

Rozsa et al., 2006) and were genotyped for the 5HTTLPR polymorphism.

The original interview version of the TEMPS-A (Temperament Evaluation of

Memphis, Pisa, Paris and San Diego) questionnaire was developed in Memphis (Akis-

kal et al., 1998; Akiskal and Akiskal, 1992) and validated in interview form in Pisa

(Akiskal et al., 1998), and ultimately in autoquestionnaire version. In the English ver-

sion, it exists in longer clinical (Akiskal et al., 2005a) and shorter research (Akiskal et

al., 2005b) formats. The recently standardised Hungarian version is the complete, un-

abridged TEMPS-A (Rózsa et al., 2006). The questionnaire measures affective tem-

peraments in five scales: depressive, cyclothymic, hyperthymic, irritable and anxious.

56

5.2 Genotyping

DNA was obtained from all subjects by buccal swabs (Walsh et al., 1991). Po-

lymerase chain reaction (PCR) amplification of 5HTTLPR was performed on genomic

DNA extracted from buccal mucosal cells. The 5HTTLPR genotypes were identified as

previously reported (Heils et al., 1996). Primers for 5HTTLPR were:

5’-GGCGTTGCCGCTCTGAATGC-3’(STPR5)

5’-GAGGGACTGAGCTGGACAACCCAC-3’

PCR was performed in a volume of 25 μL containing:

• 50 ng of genomic template

• μM of each primer

• 2.5 mM deoxyribonucleotides

• 10 mM tris-HCl (pH 8.3)

• 50 mM KCl

• 1.5 mM MgCl2

• 0.01% bovine albumin

• 1U of Taq DNA polymerase (Eurogenetech).

The cycling conditions were as follows:

1. initial denaturation at 94 oC for 5 minutes

2. 35 cycles of amplification:

i. denaturation at 95 oC for 30s

ii. annealing at 65 oC for 30s

iii. synthesis at 72 oC for 60s

3. Final extension at 72 oC for 10 min.

PCR was conducted in a Perkin-Elmer GeneAmp 2400 thermal cycler. The am-

plification products were resolved on an 8% non-denaturating polyacrylamide gel by

electrophoresis and visualized by silver staining (Figure 2). Fragment sizes were deter-

mined by comparison with molecular length standards (100 bp ladder, Invitrogen)

57

FIGURE 2. Detection of 5HTTLPR genotypes

5.3 Statistical analyses

5.3.1 General aspects

All statistical analyses were carried out using Statistica 7.0 for Windows. In all

cases our subjects were divided into genotype groups (subjects with either of the 3 dif-

ferent genotypes: ss, sl, ll) and phenotype groups (subjects carrying the s allele and sub-

jects not carrying the s allele). We compared test scores in the sample according to both

types of distribution of the subjects.

Deviations from the Hardy-Weinberg equilibrium were calculated for each sam-

ple.

5.3.2 Association of the 5HTTLPR polymorphism with subthreshold de-

pression and affective temperaments

Analysis of variance was used to determine the difference of the test scores be-

tween the three different genotype groups and the two phenotype groups. Tukey Honest

Significant Distance Tests were used for post hoc comparisons. 0.05 was accepted as

the level of significance. Mean ± SEM of the data are presented.

ss sl ll

58

5.3.3 Association of the 5HTTLPR with migraine and anxiety

Yates’ corrected chi-square test was used to test for the distribution of alleles

and genotypes in case of migraineurs and non-migraineurs. MANOVA and ANOVA

tests were used to test for the difference of psychometric scores between migraineurs

and non-migraineurs and between subjects carrying and not carrying the s allele. Tukey

Honest Significant Distance Tests were used for post hoc comparison.

6. RESULTS

6.1 The association of the 5HTTLPR and anxiety

6.1.1 The distribution of the alleles and genotypes in our sample

The distribution of alleles in our sample followed the Hardy-Weinberg equilib-

rium (χ2=0.1409, df=2, p=0.9320). The frequency of the s allele was 44.84% in the

whole sample, which parallels the results of Heils (Heils et al., 1996) and is representa-

tive of the Caucasian population.

6.1.2 Association of the 5HTTLPR s allele with trait and state anxiety

Mean scores on both scales of the STAI were not elevated compared to the Hun-

garian healthy average score. Age of migraineurs and non-migraineurs in our sample

did not differ (41.73±1.41 vs. 42.00±1.70 in migraineurs and non-migraineurs, respec-

tively).

TABLE 2. State and trait anxiety scores of subjects within the three different genotype

groups (ss, al and ll)

Mean score (±SE) 5HTT N State anxiety Trait anxiety

ss 18 35,00 (±1,98) 2,18 (±2,18)

59

sl 51 38,84 (±1,20)* 41,86 (± 1,22)ll 28 32,46 (±1,27) 38,21 (± 1,53)

* p<0.05 compared to ll genotype

In our sample subjects carrying the s allele (sl and ss genotype) scored signifi-

cantly higher on the state anxiety scale than subjects not carrying the s allele (ll geno-

type) (F=7.6288, df=1, p=0.0069, Figure 3). A strong tendency emerged for subjects

carrying the s allele to have a higher trait anxiety (F=3.2032, df=1, p=0.0767, Figure 4).

In case of the three genotype groups, a significant difference emerged between the three

groups (F=5.9462, df=2, p=0.0037, Table 2). Post hoc Tukey Honest Significant Dis-

tance test revealed that subjects carrying the sl genotype scored significantly higher than

subjects with the ll genotype (p=0.0032). There was no significant difference between

the three groups on the trait anxiety scale (F=1.6326, df=2, p=0.2009).

FIGURE 3. State anxiety scores of subjects not carrying the s allele and subjects carry-

ing the s allele in the whole sample (mean ± SE)

0 10.03031323334353637383940

5HTTLPR s allele

Stat

e An

xiet

y

0 – subjects not carrying the s allele 1 – subjects carrying the s allele

* p<0.05

*

60

FIGURE 4. Trait anxiety scores of subjects not carrying the s allele and subjects carry-

ing the s allele in the whole sample (mean ± SE)

0 10.03536373839404142434445

5HTTLPR s allele

Trai

t Anx

iety


^ p<0.077

The MANOVA test indicated a significant association between the genotype and

the psychometric measures in our sample (F=4.0605, df=2, p=0.0204). There was, how-

ever, no significant difference in this association between the diagnostic groups (mi-

graineurs vs. non-migraineurs, F=0.2802, df=2, p=0.7563) in either of the STAI sub-

scales. Differences on the anxiety scales emerged within the two diagnostic groups with

respect to the presence of the s allele. Migraineurs carrying the s allele scored signifi-

cantly higher on the State Anxiety Scale compared to migraineurs not carrying the s

allele (p=0.0338, Figure 6), and non-migraineurs carrying the s allele showed a strong

tendency to score higher on the state anxiety scale than non-migraineurs with no s allele

(p=0.0678, Figure 6). In case of the Trait Anxiety Scale, there was no significant differ-

ence between any of the subgroups studied (Figure 5).

^

61

FIGURE 5. Trait anxiety scores in non-migraineurs carrying and not carrying the s al-

lele and migraineurs carrying and not carrying the s allele (mean ± SE)

1 2 3 40.03536373839404142434445

5HTTLPR s allele and migraine

Trai

t Anx

iety

1-migraineur no s allele 2-migraineurs s allele

3-non-migraineur no s allele 4 – non-migraineur s allele

FIGURE 6. State anxiety scores in non-migraineurs carrying and not carrying the s al-

lele and migraineurs carrying and not carrying the s allele (mean ± SE)

1 2 3 40.029303132333435363738394041

5HTTLPR s allele and migraine

Stat

e An

xiet

y

* ̂ *

62

1-migraineur no s allele 2-migraineur s allele

3-non-migraineur no s allele 4-non-migraineur s allele

* p<0.05 compared to migraineur-no s allele group (1)

^ p<0.068 compared to non-migraineur no s allele group (3)

6.2 Association of the 5HTTLPR s allele with subthreshold de-pression

6.2.1 The representativness of the sample and distribution of alleles and

genotypes

All subjects in our sample had Zung Self-rating Depression Scale scores below

the level indicating depression (48 points). The mean score in the whole sample was

35.81 which corresponds to the Hungarian healthy average score (34.4) (Simon, 1998).

Frequency of the s allele was 41.4%, which corresponds to the results of previ-

ous studies (Lesch et al., 1996, Juhasz et al., 2003a; Juhasz et al., 2003b) and is repre-

sentative of the Caucasian population. The distribution of genotypes in our study popu-

lation followed the Hardy-Weinberg equilibrium (χ2=0.2446, p>0.75).

6.2.2 The association of Zung Self-rating Depression Scale scores with

phenotype

Subjects carrying the s allele (sl and ss genotypes) had a significantly higher

score on the Zung Self-rating Depression Scale (F=5.0162, df=1, p=0.0268, Figure 7)

and also had a significantly higher score on the Physical-vegetative Symptoms Subscale

(F=7.3804, df=1, p=0.0075, Figure 8) but not on the remaining items of the scale

(F=2.0830, df=1, p=0.1514, Figure 9).

63

6.2.3 The association of Zung Self-rating Depression Scale with genotype

There was a significant difference on the Zung Self-rating Depression Scale

(F=3.4490, df=2, p=0.0348) and on the Physical-vegetative Symptoms Subscale

(F=3.9384, df=2, p=0.0219) when the three different genotype groups were compared

(Table 3). No significant difference occurred in case of the remaining items of the scale

(F=2.0191, df=2, p=0.1371, Table 3). Post-hoc Tukey Honest Significant Distance Test

indicated that there was a significant difference between the ss and the ll genotype in the

case of the Total score on the Zung Self-rating Depression Scale, with the ss group scor-

ing higher (p=0.0292). There was also a significant difference between ll and sl

(p=0.0487), and ll and ss genotypes (p=0.0407) on the Physical-vegetative Symptoms

Subscale, in both cases the ll group had the lower scores.

TABLE 3. ZSDS scores according to genotype. Total and Physical-vegetative Subscale

scores of subjects within the three different genotype groups (ss, sl and ll)

Mean (±SE) 5HTT N Total ZSDS Physical-vegetative subscale Remaining items ss 21 38,14 (±1,50)* 14,76 (±0,56)* 23,38 (±1,03) sl 65 36,14 (±0,76) 14,31 (±0,32)* 21,83 (±0,59) ll 42 34,14 (±0,74) 13,14 (±0,35) 21,00 (±0,57)

*p<0.05 compared to ll genotype

64

FIGURE 7. Zung Self-rating Depression Scale scores of subjects carrying the s allele

and subjects not carrying the s allele (mean ± SE)

0 10.032

33

34

35

36

37

38

39

40

5HTTLPR s allele

Zung

Tot

al S

core


* p<0.05

FIGURE 8. Physical vegetative subscale scores of subjects carrying the s allele and sub-

jects not carrying the s allele (mean ± SE)

0 10

12.5

13.5

14.5

15.5

5HTTLPR s allele

Zung

Phy

sica

l-veg

etat

ive

sym

ptom

s su

bsca

le


* p<0.05

*

*

65

FIGURE 9. Remaining items scores of subjects carrying the s allele and subjects not

carrying the s allele (items remaining after removing physical and vegetative items)

(mean ± SE)

0 10.0

20.0

20.5

21.0

21.5

22.0

22.5

23.0

23.5

24.0

5HTTLPR s allele

Rem

aini

ng it

ems


6.3 Association of affective temperaments with the 5HTTLPR s allele

6.3.1 Distribution of alleles and genotypes in our sample

The frequency of the s allele in the sample was 38.1%, which corresponds to the

results of previous studies and is representative of the Caucasian population (Lesch et

al., 1996, Juhasz et al., 2003a; Juhasz et al., 2003b). The distribution of genotypes in our

study population followed the Hardy-Weinberg equilibrium (χ2=0.0089, p>0.95).

6.3.2 Association of the 5HTTLPR with affective temperaments with phe-

notype

We found a significant association between the phenotype groups and the

TEMPS scores in case of four of the five affective temperaments studied. Subjects car-

rying the s allele scored significantly higher in all four of these temperaments: depres-

66

sive (F=3.9812, df=1, p=0.0480, Figure 10), cyclothymic (F=4.8107, df=1, p=0.0299,

Figure 11), irritable (F=4.0041, df=1, p=0.0474, Figure 13), anxious (F=3.9607, df=1,

p=0.0486, Figure 14. No significant difference between the two phenotype groups was

found in case of the hyperthymic temperament (F=0.3302, df=1, p=0.5665, Figure 12).

TABLE 4. TEMPS-A scores according to genotype: subscale scores of subjects within

the three different genotype groups (ss, sl and ll)

* p<0.05 compared to ll genotype

FIGURE 10. TEMPS-A depressive temperament scores of subjects carrying and not

carrying the s allele (mean ± SE)

0 10

5.0

5.5

6.0

6.5

7.0

7.5

8.0

8.5

5HTTLPR s allele

Dep

ress

ive

tem

pera

men

t


* p<0.05

Mean (±SE) 5HTT N depressive cyclothymic hyperthymic irritable anxious sl 66 7.18(±0.43) 6.48 (±0.53)* 10.06 (±0.47) 4.88 (±0.45) 7.90 (±0.67)ll 53 6.32 (±0.39) 4.57(±0.47) 10.43 (±0.60) 3.43 (±0.41) 6.51(±0.66) ss 20 7.15 (±0.56) 4.95 (±0.75) 9.70 (±0.77) 4.05 (±0.74) 8.65 (±1.12)

*

67

FIGURE 11. TEMPS-A cyclothymic temperament scores of subjects carrying and not


0 10.04.0

4.5

5.0

5.5

6.0

6.5

7.0

5HTTLPR s allele

Cyc

loth

ymic

tem

pera

men

t


* p<0.05

FIGURE 12. TEMPS-A hyperthymic temperament scores of subjects carrying and not


0 10.09.0

9.5

10.0

10.5

11.0

11.5

5HTTLPR s allele

Hyp

erth

ymic

tem

pera

men

t


*

68

FIGURE 13. TEMPS-A irritable temperament scores of subjects carrying and not car-

rying the s allele (mean ± SE)

0 10.02.5

3.0

3.5

4.0

4.5

5.0

5.5

5HTTLPR s allele

Irrita

ble

tem

pera

men

t


* p<0.05

FIGURE 14. TEMPS-A anxious temperament scores of subjects carrying and not car-

rying the s allele (mean ± SE)

0 10.05.5

6.0

6.5

7.0

7.5

8.0

8.5

9.0

9.5

5HTTLPR s allele

Anxi

ous

tem

pera

men

t


* p<0.05

*

*

69

6.3.3 The association of affective temperament with genotype

When the 3 genotype groups were compared, a significant difference between

the 3 groups emerged on the scale measuring the cyclothymic temperament (F=3.8899,

df=2, p=0.0228, Table 4). Post hoc Tukey HSD test revealed that there is a significant

difference between the ll and sl groups (p=0.0080). A strong trend (F=2.6815, df=2,

p=0.0721) was observed in case of the irritable temperament, with post hoc Tukey HSD

test indicating that subjects with sl genotype had a significantly higher score than sub-

jects with ll genotype (p=0.0227). No significant association emerged in case of the

other three temperaments: depressive (F=1.2320, df=2, p=0.2950, Figure 2), hyper-

thymic (F=0.2737, df=2, p=0.7610), anxious (F=1.6910, df=2, p=0.1882) (Table 4).

7. DISCUSSION

7.1 The serotonin transporter gene and anxiety

7.1.1 Trait and state anxiety and the s allele

Previous studies have demonstrated a significant positive association between

the s allele of the 5HTTLPR gene and well-defined anxiety disorders (Ohara et al.,

1998). It has also been reported that the s allele of the 5HTTLPR was associated with

anxiety-related traits such as neuroticism and harm avoidance (Lesch et al., 1996; Ka-

tsuragi et al., 1999). Our finding that in the whole sample higher state anxiety scores

were significantly associated with the s allele of the 5HTTLPR in a healthy population

without any lifetime or current DSM-IV Axis I disorder supports and extends these re-

sults and suggests that the relationship between the s allele and anxiety is present even

in a population with subthreshold level of psychopathology. Although we have ex-

cluded subjects with any lifetime and current DSM-IV Axis I disorders, it is very likely

70

that our population contained several subjects with subthreshold anxiety symptoms that

share many biological, genetic and clinical characteristics with the full-blown, DSM-IV

defined anxiety disorders. The fact that a significant relationship emerged only in case

of the state anxiety scale, while for trait anxiety a strong tendency was present, indicates

that this relationship between anxiety and the s allele is stronger in case of anxiety as a

way of reacting to stressful and unpleasant anxiety-provoking situations rather than a

constant level of increased anxiety. It should also be mentioned, however, that in case of

the trait anxiety scale, a strong trend for the association with the s allele emerged, which

supports that this allele plays a significant role in the background of anxiety in general.

7.1.2 The association of anxiety, migraine and the s allele

Our population in the study investigating the association between anxiety and

the s allele also included migraine without aura patients. Migraineurs have classically

been described as characterised by increased mood lability, depression, panic, phobia,

inflexibility and perfectionism (Wolff, 1965). In addition, these data are in good agree-

ment with most recent findings that migraineurs score higher on Eysenck’s neuroticism

scale (Breslau et al., 1991) and that migraine is frequently associated with anxiety and

depressive disorders (Breslau et al., 1991; Oedegaard and Fasmer, 2005).

Our data provide evidence that psychiatrically healthy migraineurs carrying the s

allele do not have higher anxiety compared to non-migraineurs carrying the s allele.

This means that migraine in itself may not be associated with increased anxiety. Our

results suggest that the observation that anxiety and anxiety-related personality is more

frequent among migraineurs can be explained by the higher rate of persons carrying the

s allele in migraineurs, which in turn is associated with higher anxiety.

71

7.2 The serotonin transporter gene and subthreshold depres-sion

The aim of our study was to establish whether, similarly to major mood disor-

ders, there is an association between the s allele of the serotonin transporter gene

5HTTLPR polymorphism and subthreshold depression and depressive traits within a

healthy population. The main result of our study is that in a psychiatrically healthy

population depression scores show a significant association with the s allele of the sero-

tonin transporter gene 5HTTLPR polymorphism. This result suggests that subclinical

forms of depression are a part of the same continuum as other, DSM-IV defined affec-

tive disorders which have also been found to be related to this polymorphism (Bellivier

et al., 1998; Hauser et al., 2003; Lotrich and Pollock, 2004). The genetic and biological

background of depressive traits and subclinical forms of depression have not been ex-

tensively studied so far, despite the fact that these disorders affect a significant portion

of the population and cause substantial subjective suffering as well as social and work

impairment. In our study we also found that a subscale consisting of only the items re-

ferring to the physical and vegetative symptoms of depression also shows association

with the s allele of the 5HTTLPR polymorphism. In case of the remaining items of the

scale this association disappears, which suggests that mainly physical and vegetative

symptoms might carry the relationship between this polymorphism and subclinical

forms of depression.

Given the high prevalence of subsyndromal depressive disorder in the popula-

tion it is very likely that our sample included several subjects suffering from this condi-

tion and these subjects do not fulfil the criteria of any “threshold” DSM-IV disorders,

such as major depression, dysthymic disorder or minor depression. In agreement with

this, the scores of these subjects on the Zung Self-rating Depression Scale were below

the level indicating clinical depression but people suffering from subthreshold forms of

depression were not excluded. In conclusion, our data suggest that subclinical (sub-

threshold) depressive disorders have the same genetic association with the serotonin

transporter gene as DSM-IV defined major mood disorders. This is not surprising, since

previous follow-up studies have shown that more than 25% of patients with subsyndro-

mal depression develop major mood disorders in two years (Sherbourne et al., 1994)

72

and subsyndromal depression responds to antidepressants similarly as major depression

(Rapaport and Judd, 1998). The syndrome measured by the Physical-vegetative Symp-

toms Subscale within the original ZSDS overlaps with subsyndromal depressive disor-

der without mood disturbances, as described by Judd (Judd et al., 1994). Our results

thus indicate that physical and vegetative symptoms of subsyndromal depression by

themselves may carry this association with the s allele of the serotonin transporter gene.

7.3 The association of the serotonin transporter gene with af-fective temperaments

In line with earlier reports on the strong association between the s allele of the

5HTTLPR polymorphism of the serotonin transporter gene and major depression (Bel-

livier et al, 1998, Hauser et al, 2003, Lotrich and Pollock, 2004), as well as subthreshold

depression (Gonda et al, 2005), our present findings suggest the same connection re-

garding the depressive component of personality even at the normative temperament

level. The increased vulnerability for depression after stressful life events among people

carrying the s allele has also been demonstrated in a prospective-longitudinal study

(Caspi et al., 2003). Overall these data and considerations suggest that the affective

temperaments under investigation are best conceived as behavioural endophenotypes in

genetic research focusing on affective disorders.

Our results showed that affective temperaments carrying a depressive compo-

nent (depressive, cyclothymic, irritable and anxious) are significantly associated with

the s allele, while there was no such association in case of the hyperthymic tempera-

ment. At least two studies (Placidi et al., 1998; Akiskal et al., 2005a) have shown that

mood-labile depressive (and possibly irritable), temperaments aggregate into a “super

factor” of cyclothymia which is distinct from the hyperthymic “super factor.” Whenever

the anxious subscale of TEMPS-A was studied, its cognitive subscale strongly corre-

lated with that of the depressive (Erfurth et al., 2005; Vahip et al., 2005). In other

words, psychometric aggregation of temperaments (the depressive, anxious, irritable

and cyclothymic) finds molecular genetic support in their association with the s allele of

73

5HTTLPR, indicating that these temperament, although grab different aspects of affec-

tive lability and emotional reactivity, are all basically related, such as depressiveness

and anxiety, to neuroticism. We submit, however, that our data are more cogent, be-

cause neuroticism is a global construct which subsumes, among others, such traits as

anxiousness, depressiveness, and mood lability (Eysenck, 1987). The TEMPS-A scales

more specifically and individually measure each of the foregoing trait dimensions.

7.4 The association of the 5HTTLPR s allele with a low/ labile mood high anxiety endophenotype within a psychiatrically healthy population

In the neurochemical background of all the above phenomena (anxiety, depres-

sion and increased affective reactivity, and also migraine) the role of the serotonergic

system is suspected and the serotonin transporter gene is one possible candidate. These

psychological phenomena, however, have a polygenic multifactorial background and

the phenotype develops in interaction with other genes and the environment. It may be

that if the function of the serotonergic system is altered due to the polymorphism of the

serotonin transporter gene, this results in the formation of some combination of the

three possible symptoms depending on the other interacting factors.

Our results suggest that increased affective lability, anxiety and depression are

part of a spectrum of the manifestations of an abnormality in the 5HT-metabolism due

to a polymorphism in the 5HTTLPR gene. The severity of these symptoms might not

reach the criteria of psychiatric diseases, but the presence of more than one of the symp-

toms may indicate a more problematic case, sometimes even the manifestation of a psy-

chiatric disorder. Affective and anxiety disorders have a tendency to occur together as

comorbidity (Rihmer et al., 2001). Migraine is also a frequently comorbid condition of

these disorders (Oedegard and Fasmer, 2005). When the three disorders (anxiety, de-

pression and migraine) appear together, there is a temporal association of the disorders

characterised by the early onset of an anxiety disorder, followed later by the develop-

74

ment of migraine and then the development of depression (Merikangas and Stevens,

1997).

7.5 The serotonin transporter gene and neuroticism

Our results indicate that a low / labile mood, high anxiety endophenotype can be de-

scribed within a healthy population and linked to a polymorphism in the 5HTTLPR

gene. This description is similar to the classical description of people scoring high on

the scales measuring neuroticism. Our studies, however, found evidence that all of the

mentioned aspects of neuroticism play a role in the association of neuroticism and the s

allele of the 5HTTLPR. This polymorphism therefore is associated not only with psy-

chiatric disorders, but also well-definable personality characteristics important in the

constitution of personality. This further emphasises the need for future research to de-

lineate the genetic background of traits and characteristics observable in the healthy

population as endophenotypes related to neuropsychiatric disorders.

It is important to note that all our subjects were female, so it needs further inves-

tigation whether our results are also valid in males. The symptoms and disorders we

studied are significantly more common among women (Weissman and Olofson, 1995;

Piccinelli, 2000; Breslau and Rasmussen, 2001; Pigott, 1999). There are also gender

differences in the function of the serotonergic system, and this difference occurs both at

the level of receptors and metabolism (Arató and Bagdy, 1998; Bagdy, 1998; Charney

et al., 1988; Heninger, 1997). Further experiments should be carried out to identify the

effect of the 5HTTLPR polymorphism on anxiety, depression and affective reactivity in

men.

75

8. CONCLUSIONS

The results of our research, which has focused on the relationship between the s allele of

the 5HTTLPR polymorphism and depression, anxiety and affective temperaments, lead

us to the following conclusions:

• The s allele of the serotonin transporter gene is significantly associated with sub-

threshold forms of depression in a psychiatrically healthy sample. The s allele of

the 5HTTLPR shows even stronger association with subthreshold depression if

only the physical and vegetative symptoms associated with depression are taken

into account. This result suggests that physical and vegetative symptoms might

carry the association between the 5HTTLPR s allele and subthreshold depres-

sion.

• The s allele of the 5HTTLPR is significantly associated with state anxiety, and

there is a strong tendency in case of trait anxiety. This result points to the asso-

ciation of the s allele and anxiety in general, but it also emphasises that this as-

sociation in case of the s allele is not primarily valid for a constant increased

level of anxiety, but rather for anxiety proneness and stress sensitivity.

• The s allele of the 5HTTLPR is significantly associated with those affective

temperaments which carry a depressive component (depressive, cyclothymic,

anxious, irritable), but not with the hyperthymic temperament. This result

strengthens the association of the s allele with affective lability.

• Our results indicate that the s allele is significantly associated with several inde-

pendent facets, such as anxiety, anxiety proneness, depressiveness, tendency for

depression to manifest in the form of physical and vegetative symptoms and af-

fective lability, which comprise the neuroticism / emotional lability personality

dimension. Our research thus supports the relationship between neuroticism and

s allele, and indicates that neuroticism as a whole and solid construct and not

only one of its factors is responsible for this association. Our results thus indi-

cate that neuroticism is also genetically (and not only phenomenologically) a

solid construct.

76

• Our results have important implications for everyday clinical practice and the

way psychiatric disorders are viewed. It seems reasonable from our research that

the category of neurosis and neurotic disorders, which is not used in modern

classification systems, might be considered solid from a genetic point of view.

• Our results can also be viewed from the aspect of gene-environment interac-

tions: the strong presence of affective temperaments themselves and neuroticism

may confer an increased vulnerability to chronic stress and other life events that

play an important causal role in the emergence of depression, and thus preven-

tive psychological and biological therapies may be helpful in people carrying the

s allele and subjected to chronic stress.

• Furthermore, our findings open the potential to identify within the community

those people with temperamental inclination to mood instability with the joint

use of measures of putative behavioural endophenotypes and molecular genetic

markers. Given that 20-30% of the population is at risk for affective spectrum

disorders based on temperamental vulnerability (Akiskal et al., 1998; Akiskal

and Akiskal, 2005), and given that 60–70% of the population appears to carry

the s allele, which under permissive “stressful” circumstances might express

clinical affective phenotypes (Caspi et al., 2003), the present findings bring psy-

chiatric genetics closer to the aim of delineating risk profiles for such expression

in more precise quantitative measures. This further emphasises the need for fu-

ture research to delineate the genetic background of traits and characteristics ob-

servable in the healthy population as endophenotypes related to neuropsychiatric

disorders.

77

9. SUMMARY

9.1 Summary

We investigated the association of the 5HTTLPR polymorphism of the serotonin

transporter gene and anxiety, depression and affective temperaments in a psychiatrically

healthy female population. The association of this polymorphism has earlier been de-

scribed in case of psychiatric disorders (anxiety and affective disorders). In case of a

healthy population, however, mainly its association with the neuroticism trait was ex-

amined. Our aim was to investigate the association of subclinical manifestations of de-

pression and anxiety and possible association of affective temperaments with the above

polymorphism. In case of the neuroticism trait an association with 5HTTLPR has earlier

been demonstrated. Neuroticism, however, is a complex trait incorporating tendency for

anxiety, depression, irritability and mood lability, and thus it wasn’t obvious whether all

the above psychological phenomena equally contribute to the association of neuroticism

and the s allele, or only some of these play a crucial role in this relationship.

In our research we administered questionnaires assessing depression (ZSDS,

Zung Relf-rating Depression Scale), anxiety (STAI, State-Trait Anxiety Inventory) and

affective temperaments (TEMPS-A, Temperature Evaluation of Memphis, Pisa, Paris

and San Diego), and determined 5HTTLPR genotype by means of polymerase chain

reaction (PCR).

We found that depression, anxiety and affective temperaments carrying a de-

pressive component (depressive, cyclothymic, anxious, irritable) show significant asso-

ciation with the s allele of the 5HTTLPR, indicating that people carrying the s allele are

more prone to increased anxiety, depression and are more likely to carry one of the af-

fective temperament-types incorporating a depressive component. Furthermore, if only

physical and vegetative symptoms of depression are taken into consideration this asso-

ciation was even stronger, indicating that physical and vegetative symptoms of depres-

sion are also strongly associated with the s allele.

Viewed from the aspect of gene-environment interactions our results show that

the presence of dominant affective temperaments and personality traits related to neu-

78

roticism confers increased vulnerability to chronic stress and other life events which

play an important causative role in the development of depression. Our findings open

the potential to identify within the community people with temperamental inclination to

mood instability with the joint use of measures of putative behavioural endophenotypes

and molecular genetic markers. The present findings bring psychiatric genetics closer to

the aim of delineating risk profiles for clinically manifested affective disorders in more

precise quantitative measures and thus point to the possibility of preventive psychologi-

cal and biological therapies. This further emphasises the need for future research to de-

lineate the genetic background of traits and characteristics observable in the healthy

population as endophenotypes related to neuropsychiatric disorders.

79

9.2 Összefoglalás

Kutatásunk során a szerotonin transzporter gén egyik funkcionális polimorfiz-

musa (5HTTLPR), valamint a szorongásra való hajlam, a depresszióra való hajlam és az

affektív temperamentumok összefüggését vizsgáltuk egészséges populációban. Koráb-

ban a fenti polimorfizmus összefüggését írták le pszichiátriai kórképekkel (szorongásos-

és hangulatzavarok), azonban pszichiátriai szempontból egészséges populációban első-

sorban a neuroticizmussal való összefüggését vizsgálták. Célunk az volt, hogy a szoron-

gás és a depresszió szubklinikus formáinak együttjárását, valamint az affektív tempera-

mentumok esetleges összefüggéseit vizsgáljuk a fentebbi polimorfizmus esetében. A

neuroticizmus vonással kapcsolatban korábban sikerült összefüggést kimutatni az

5HTTLPR polimorfizmussal, azonban mivel a neuroticizmus olyan komplex személyi-

ségvonás, amely magában foglalja a depresszióra és szorongásra való hajlamot, az

irritabilitást és a hangulati labilitást, nem volt egyértelmű, hogy mindezen pszichológiai

jelenségek egyaránt hozzájárulnak a neuroticizmus és az s allél kapcsolatához, vagy

ezek közül csak néhány játszik kiemelt szerepet a leírt összefüggésben.

Vizsgálataink során a depressziót (ZSDS, Zung Önértékelő Depresszió Kérdő-

ív), a szorongást (STAI, Spielberger-féle Vonás- és Állapotszorongást mérő Kérdőív) és

az affektív temperamentumokat (TEMPS-A) mérő személyiségteszteket alkalmaztunk, a

genotípust pedig polimeráz láncreakció (PCR) segítségével határoztuk meg.

Kutatásunk során azt találtuk, hogy a depresszió, a szorongás, és a depresszív

komponenst is hordozó affektív temperamentumok (depresszív, ciklotím, szorongó,

irritábilis) szignifikáns összefüggést mutattak az 5HTTLPR s alléllal, azaz az s variánst

hordozók hajlamosabbak a fokozott szorongásra, a depresszióra, és nagyobb valószínű-

séggel tartoznak valamelyik, depresszív komponenst hordozó temperamentumcsoport-

ba. Továbbá, ha csak a depresszió fizikai és vegetatív tüneteit vettük figyelembe, az

összefüggés még erősebbnek mutatkozott. Ez arra utal, hogy a depresszió fizikai és ve-

getatív tünetei szintén szoros összefüggésben állnak az s alléllal.

A gén-környezet interakciók irányából megközelítve kutatásaink arra utalnak,

hogy a domináns affektív temperamentumok, illetve a neuroticizmussal összefüggő

személyiségvonások megléte fokozott sérülékenységet eredményez a krónikus stresszel

és egyéb életeseményekkel szemben, amelyek fontos oki szerepet játszanak a depresszió

80

kialakulásában. Eredményeink alapján felmerül annak lehetősége is, hogy a viselkedé-

ses endofenotípusokkkal kapcsolatos ismereteink és a molekuláris genetikai markerek

segítségével a populációban azonosítsuk azokat, akik temperamentumuk alapján foko-

zottan hajlamosak a hangulatzavarokra. Eredményeinkkel közelebb kerülhetünk a pszi-

chiátriai genetika azon célkitűzéséhez, hogy precízebb kvantitatív módszerek segítségé-

vel tárjuk fel a hangulatzavarok szempontjából fokozott rizikót hordozó személyiség-

profilokat. Így felmerül a megelőző pszichoterápiák és biológiai terápiák lehetősége is.

Ez a megközelítés ugyanakkor hangsúlyozza az egészséges populációban megfigyelhető

vonások és temperamentumok, mint neuropszichiátriai betegségekkel kapcsolatos

endofenotípusok genetikai hátterének feltárásával kapcsolatos további kutatások szük-

ségességét.

81

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11. PUBLICATIONS

11.1 Publications relevant to the dissertation

11.1.1 Journal articles

1. Gonda, X., Rihmer, Z., Juhasz, G., Zsombok, T., Bagdy, G. (2007) High anxiety

and migraine are associated with the s allele of the 5HTTLPR gene polymor-

phism. Psychiatry Res,149: 261-6

2. Gonda X, Rihmer, Z, Zsombok, T, Bagdy G, AKiskal, KK, Akiskal HS. (2006)

The 5HTTLPR polymorphism of the serotonin transporter gene is associated

with affective temperament as measured by TEMPS-A. J Affect Disord, 91:

125-131.

3. Gonda X, Juhasz G, Laszik A, Rihmer Z, Bagdy G. (2005) Subthreshold depres-

sion is linked to the functional polymorphism of the 5HT transporter gene. J Af-


4. Gonda X, Bagdy G. (2003) A szerotonin mint az agresszió biológiai kor-

relátuma. Neuropsychopharmacol Hung, 5: 125-132.

5. Gonda X, Bagdy G. (2004) A premenstruális szindróma és a szerotonerg funk-

ciók összefüggései. Neuropsychopharmacol Hung, 6:153-162.

6. Gonda X, Bagdy G. (2007) A szerotonin transzporter gén 5HTTLPR polimor-

fizmusának összefüggése a neuroticizmus tüneteivel egészséges populációban.

Psychiatr Hung, 149: 261-266.

7. Juhasz G, Zsombok, T, Laszik, A, Gonda, X, Sotonyi, P, Faludi, G, Bagdy G.

(2003) Association analysis of 5-HTTLPR variants, 5-HT2A receptor gene

102T/C polymorphism and migraine. J Neurogenet, 17: 231-240.

107

8. Rihmer Z, Gonda X, Akiskal KK, Akiskal HS. (2007). Affective temperament: a

mediating variable between environemtn and clinical depression? Letter to the

editor. Arch Gen Psychiatry, in press.

9. Rózsa S, Rihmer A, Kő, N, Gonda X, Szili I, Szádóczky E, Pestality P, Rihmer

Z. (2006) Az affektív temperamentum: a TEMPS-A kérdőívvel serzett hazai

tapasztalatok. Psychiatr Hung, 21: 147-160.

10. Rozsa S, Rihmer Z, Gonda X, Szili I, Rihmer An, Ko N, Nemeth A, Pestality P,

Bagdy G, Alhasoon O, Akiskal KK, Akiskal HS. A Study of Affective Tem-

peraments in Hungary: Internal Consistency and Concurrent Validity of the

TEMPS-A against the TCI and NEO PI-R. J Affect Disord, in press.

11.1.2 Posters and presentations:

11. Gonda X, Bagdy G. (2004) A szerotonin transzporter gén funkcionális polimor-

fizmusának összefüggése a migrénnel és a szorongással. Poszter. A Semmelweis

Egyetem IV. Interdiszciplináris Mentális Egészségtudományok Doktori Iskola

X. Tudományos Ülése. Budapest, 2004. november 3. Absztraktkötet: 8.

12. Gonda X, Juhasz G, Zsombok T, Bagdy G. (2004) Migraineurs carry an

increased frequency of the 5HTTLPR s allele and show higher anxiety. Poszter.

A Magyar Pszichofarmakológiai Társaság VII. Kongresszusa. Tihany, 2004.

szeptember 30-október 2. Absztrakt: Neuropsychopharmacol Hung, 6: 29.

13. Gonda X, Juhász G, Zsombók T, Lászik A, Bagdy G. (2005) A szorongás és a

szerotonin transzporter gén s alléljának összefüggése migrénesekben és egészsé-

ges személyekben. Poszter. Semmelweis Egyetem Doktori Iskola Tudományos

Napok. Budapest, 2005. április 14-15. Absztraktkötet: 110.

14. Gonda X, Juhász G, Zsombók T, Lászik A, Bagdy G. (2005) Fokozott szorongás

a szerotonin transzporter gén s allélját hordozó személyekben. Poszter. A Ma-

108

gyar Pszichiátriai Társaság Jubileumi XII. Vándorgyűlése. Budapest, 2005. ja-

nuár 26-30. Absztrakt: Psychiatr Hung, 19: 50.

15. Gonda X, Juhász G, Bagdy G. (2005) Association of depression with the s allele

of the 5HTTLPR: Implications towards pharmacotherapy. Poster. Pharmacy:

Smart molecules for therapy. Poszter. Magyar Tudományos Akadémia, Buda-

pest, 2005. október12-14, 2005.

16. Gonda X, Bagdy G. (2005) A szerotonin transzporter gén polimorfizmus és a

depresszióra való hajlam összefüggése egészséges populációban. Előadás. A

Semmelweis Egyetem IV. Interdiszciplináris Mentális Egészségtudományok

Doktori Iskola XI. Tudományos Ülése. Budapest, 2005. november 24. Abszt-

raktkötet: 12.

17. Gonda X, Juhasz G, Zsombok T, Rihmer Z, Bagdy G. (2005) s allele of the

5HTTLPR: a gene associated with a low mood endophenotype in a

psychiatrically healthy population. Poszter. A Magyar Pszichofarmakológiai

Társaság VIII. Kongresszusa. Tihany, 2005. október 6-8. Absztakt:

Neuropsychopharmacol Hung 2005, 7: 29.

18. Gonda X., Kirilly E., Bagdy G. (2006) Gyógyszerválasztás genetikai markerek

alapján: s szerotonin transzporter gén és a depresszió összefüggései. Poszter.

Congressus Pharmaceuticus Hungaricus XIII. Budapest, 2006. május 25-27.

19. Gonda X, Zsombók T, Juhász G, Rihmer Z, Bagdy G. (2006) A depresszióra va-

ló hajlam genetikai háttere: A szerotonin transzporter gén szerepe. Előadás. A

Magyar Pszichiátriai Társaság VI. Nemzeti Kongresszusa, Budapest, 2006. feb-

ruár 1-4. Absztrakt: Psychiatr Hung, 20: 24.

20. Gonda X, Rihmer Z, Zsombok T, Juhasz G, Rozsa S, Bagdy G, Akiskal HS.

(2006) Depressive component of affective temperaments is linked to the

5HTTLPR polymorphism of the serotonin transporter gene. Poszter. 14th

European Congress of Psychiatry, Nice, France March 4-8, 2006. Absztrakt: Eur

Psychiatry, 21: 146.

109

21. Gonda X, Rihmer Z, Bagdy G. (2006) Affective temperaments are associated

with the s allele of the 5HTTLPR polymorphism of the serotonin transporter

gene. Poszter. A Magyar Pszichofarmakológiai Társaság IX. Kongresszusa. Ti-

hany, 2006. október 5-7. Absztrakt: Neuropsychopharmacol Hung, 8: 25.

22. Gonda X, Lazary J, Rihmer Z, Bagdy G. (2006) Physical-vegetative symptoms

of subthreshold depression are associated with the s allele of the serotonin

transporter gene. Poszter. The Second Dual Congress on Psychiatry and the

Neurosciences. Athens, December 7-10, 2006. Absztraktkötet: 80.

23. Gonda X. (2006) A szerotonin transzporter gén szerepe és a neurózis: az

5HTTLPR s allél, az affektív temperamentumok, a szorongás és a depresszióra

való hajlam összefüggése egészséges populációban. Előadás. A 4. sz. Mentális

Egészségtudományok Doktori Iskola XII. Tudományos Ülése. 2006. december

15. Absztaktkötet: 8.

24. Gonda X, Rihmer Z, Bagdy Gy. (2007) A szerotonin transzporter gén szerepe és

a neuroticizmus: az 5-HTTLPR s allél, az affektív temperamentumok, a szoron-

gás és a depresszióra való hajlam összefüggése egészséges populációban. A Ma-

gyar Pszichiátriai Társaság XIII. vándorgyűlése, Miskolc, 2007. január 24-27.

25. Gonda X, Lazary J, BagdyG. (2007): Association between factors related to risk

of suicide: hopelessness, aggression, impulsivity and the 5HTTLPR s allele.

Cambridge /Luton International Conference on Mental Health 2007. Cambridge,

October 11-13.

26. X. Gonda, J. Lazary, Z. Rihmer, G. Bagdy: The s allele of the 5HTTLPR: the

possible genetic background of physical-vegetative symptoms of subthreshold

depression. NewMood AGM Conference 2007, Budapest, 16 – 17 April, 2007.

27. J. Lazary, X. Gonda, A. Benko, G. Juhasz, G. Bagdy: Preliminary results of the

human genetic NewMood study: the Budapest and Manchester collaboration.

NewMood AGM Conference 2007, Budapest, 16 – 17 April, 2007.

110

28. Gonda X: Affective temperament: the mediating variable between environment

and clinical depression? Third International Symposium on Bipolar Disorders,

Visegrád, September 7-8, 2007.

11.2 Other publications

11.2.1 Journal articles

29. Bagdy G, Zsombok T, Gonda X, Juhasz G. (2003) Autogenic training might

help headache patients. Focus on Alternative and Complementary Therapies, 8:

345-347.

30. Dome P, Teleki Zs, Gonda X, Gaszner G, Mandl P, Rihmer Z. (2006)

Relationship between obsessive-complusive symptoms and smoking habits

among schizophrenic patients. Psychiatry Res, 144: 227-231

31. Dome P, Rihmer Z, Gonda X, Pestality P, Kovács G, Teleki Z, Mandl P.

(2005) Cigarette smoking and psychiatric disorders in Hungary. Int J Psychiatry

Clin Pract, 9:145-148.

32. Gonda X, Bagdy G. (2003) A szociális státusz hatása az agressziót meghatározó

biológiai paraméterekre. Psychiatr Hung, 18: 147-153.

33. Gonda X, Bagdy G. (2004) A premenstruális szindróma kronobiológiai össze-

függései. Psychiatr Hung, 6: 487-496.

34. Juhász G, Zsombók T, Gonda X, Bagdy G. (2004) A nitroglicerin által okozott

fejfájások. Orvosi Hetilap, 145: 2323-2328.

35. Juhasz G, Zsombok T, Gonda X, Nagyne NR, Modosne EA, Bagdy G. (2007)

Effects of autogenic training during nitroglycerin-induced headaches. Headache,

47: 371-83.

111

36. Rihmer Z, Gonda X. (2006) Az antidepresszívummal kezelt betegek öngyilkos

magatartása. Neuropsychopharmacol Hung, 8: 13-16.

37. Rihmer Z, Gonda X. (2006) A bipoláris betegségek diagnózisa és kezelése.

Hippocrates, 8:160-163.

38. Rihmer Z, Gonda X, Szókontor N. (2007) Az antidepresszívumok és az

öngyilkosság összefüggése. Gyógyszerészet, 51: 141.

39. Sebestyén B, Gonda X, Berze H, Rihmer Z. (2006) Öngyilkosság és depresszió:

az ápolók szerepe a felismerésben és megelőzésben. Nővér, 19: 13-20.

40. Sikter A, Frecska E, Braun IM, Gonda X, Rihmer Z. (2007) The role of hyper-

ventilation – hypocapnia in the pathomechanism of panic disorder. Revista

Psiquiatria Brasiliana, in press.

41. Zsombók T, Juhász G, Gonda X, Vitrai J, Bagdy G. (2005) Kognitív- és

szimbólumterápiás elemekkel módosított autogén tréning hatása az elsődleges

fejfájós betegek kezelésére. Psychiatr Hung, 7: 25-34.

11.2.2. Posters and presentations

42. Gonda X, Bagdy G. (2003) Pszichológiai és fiziológiai változások a női nemi

ciklus során. Poszter. A Semmelweis Egyetem IV. Interdiszciplináris Mentális

Egészségtudományok Doktori Iskola Tudományos Ülése. Budapest, 2003. no-

vember 29. Absztraktkötet:17

43. Gonda X, Bagdy G. (2004) A premenstruális szindróma biopszichoszociális hát-

tere. Poszter. A Magyar Pszichiátriai Társaság XI. Vándorgyűlése. Szeged,

2004. január 29. Absztrakt: Psychiatr Hung, 18: 38.

44. Graf M, Kántor S, Gonda X, Bagdy Gy. (2003) Szerotonin receptorok és szo-

rongás. Kísérletes eredmények és klinikai adatok összehasonlítása. Előadás.

112

Magyar Pszichiátriai Társaság X. Vándorgyűlése. Sopron, 2003. január 29-

február 1. Absztraktkötet: 65.

45. Graf M, Kántor S, Gonda X, Bagdy Gy. (2003) Szerotonin receptor altípusok

lehetséges szerepe egyes szorongásos zavarokban. Előadás. IV. Magyar

Viselkedésélettani Konferencia, Budapest, 2003. október 30.

46. Graf M, Kántor S, Gonda X. (2003) Szerotonin 1A és szerotonin 2C receptorok

szerepe a szorongásban. Állatkísérletes eredmények és humán vizsgálatok ösz-

szehasonlítása. Előadás. Semmelweis Egyetem Doktori Iskola PhD Tudományos

napok. Budapest, 2003. április 10-11. Absztraktkötet: 51.

47. Juhasz G, Gonda X, Zsombok T, Bagdy G. (2005) Hunting endophenotypes for

major depression: the role of co-morbid migraine and s-allele of the 5-HTTLPR.

Poszter. BAP 2005 Summer Meeting: 24 – 27 July Harrogate International Cen-

tre. Absztrakt: J Psychopharmacol, 19: A49-A49.

48. Rihmer A, Rozsa S, Rihmer Z, Gonda X. (2006) Affective temperaments in

nonviolent suicide attempters. Poszter. 14th European Congress of Psychiatry.

Nice, France March 4-8, 2006. Absztrakt: Eur Psychiatry, 21:165

49. Rihmer A, Rózsa S, Rihmer Z, Gonda X. (2006) Affektív temperamentum-

típusok nem-violens öngyilkossági kísérletet elkövetők esetében. Előadás. A

Magyar Pszichiátriai Társaság VI. Nemzeti Kongresszusa. Budapest, 2006.

február 1-4. Absztrakt: Psychiatr Hung, 20: 120.

50. Rózsa S., Rihmer, Z., Szádóczky, E., Gonda, X. (2005) Affective temperaments

is clinicaly well subjects in Hungary: Initial psychometric data on the TEMPS-

A. Előadás. Második nemzetközi szimpózium a bipoláris betegségről, Budapest,

2005. szeptember 24-25.

51. Rihmer Z, Gonda X. (2007) Declining suicide mortality in Hungary: what are

the main causes? Előadás. The Second Dual Congress on Psychiatry and the

Neurosciences. 7-10 December 2006, Athens. Absztraktkötet: 19.

113

52. Rihmer Z, Gonda X. (2006) Prediction and prevention of suicides in bipolar dis-

order. Előadás. The second dual congress on psychiatry and the neurosciences.

7-10 December 2006, Athens. Absztraktkötet :30.

53. Teleki Z, Döme P, Gonda X, Gaszner G, Mandl P, Rihmer Z. (2006) A kénysz-

eres tünetek és a dohányzási szokások összefüggésének vizsgálata szkizofré-

niában. Poszter. A Magyar Pszichiátriai Társaság VI. Nemzeti Kongresszusa,

Budapest, 2006. február 1-4. Absztrakt: Psychiatr Hung, 20: 148.

54. Rihmer A, Rozsa S, Rihmer Z, Gonda X, Akiskal KK, Akiskal HS. (2007) Af-

fective temperament-types and suicidal behaviour. Poster. 15th European Con-

gress of Psychiatry. Madrid, March 17-21, 2007. Abstract: European Psychiatry,

22, suppl 1, S244.

55. Rihmer Z, Gonda X, Rihmer A. (2007) Programs and Campaigns: Introducing

better understanding of the suicide phenomenon. Presentation. 15th European

Congress of Psychiatry. Madrid, March 17-21, 2007. Abstract: European Psy-

chiatry, 22, suppl 1, S34.

56. Kiss HG, Gonda X, Rihmer A, Seregi K, Pestality P, Kovacs D, Kecskes I,

Akiskal KK, Akiskal HS. Rihmer Z. Association of affective temperaments with

Cloninger’s biological model of personality. European College of Neuropsycho-

pharmacology 20th Annual Congress, Vienna, 13-17 October, 2007.

57. Rihmer Z, Gonda X, Rihmer A, Kiss HG, Kovács D, Pestality P, Seregi K, Kec-

skés I, Döme P. Association of smoking and suicide attempts in psychiatric

outpatients in Hungary. European College of Neuropsychopharmacology 20th

Annual Congress, Vienna, 13-17 October, 2007.

58. Zsombók T, Juhász G, Gonda X, Bagdy G. A szérum-kortizol koncentráció vál-

tozásai az NO-indukált migrénmodellben. Előadás. A Magyar Fejfájás Társaság

XIV.kongresszusa, Siófok, 2007. május 4-5.

114

11.3 Book Chapters

59. Bagdy G, Gonda X. A másnap, harmadnap kialakuló pszichés hatások. In:

Bagdy G. (ed), Amit az ecstasyról tudni kell. Akadémiai Kiadó, Budapest, 2006:

122-124.

60. Bagdy G, Gonda X, Lazáry J. A hetekkel, hónapokkal, évekkel később kialakuló

pszichés hatások. In: Bagdy G. (ed), Amit az ecstasyról tudni kell. Akadémiai

Kiadó, Budapest, 2006: 142-147.

61. Bagdy G, Gonda X, Lazáry J. Az ecstasy veszélyei. In: Bagdy G. (ed), Amit az

ecstasyról tudni kell. Akadémiai Kiadó, Budapest, 2006: 155-271.

62. Gonda X, Kirilly E. Az ecstasy története. Fogyasztási szokások a népesség kö-

rében. In: Bagdy G. (ed), Amit az ecstasyról tudni kell. Akadémiai Kiadó, Bu-

dapest: 2006:11-20.

63. Gonda X, Bagdy G. Az első néhány órában kialakuló pszichés hatások. In:

Bagdy G. (ed), Amit az ecstasyról tudni kell. Akadémiai Kiadó, Budapest, 2006:

94-98.

64. Rihmer Z, Benazzi F, Gonda X. Suicidal behavior in unipolar depression: Focus

on mixed states. In: Tatarelli R, Pompili M, Girardi P (eds), Suicide in Psychiat-

ric Disorders. Nova Publishers Inc, New York, in press.

65. Fountoulakis K, Rihmer Z, Gonda X, Kaprinis G. Suicide in unipolar major de-

pression. In: Shrivastava S (ed) Handbook of suicidal behaviour, in press.

115

12. ACKNOWLEDGEMENT

I would like to express my appreciation and gratitude to everyone who has

helped me during my research. This thesis was created with the assistance, cooperation

and support of several friends and colleagues.

First of all my gratitude is expressed to my mentor Prof. Dr. György Bagdy for

his supervision, guidance and encouragement of my work in the Laboratory of Neuro-

chemistry and Experimental Medicine, National Institute for Psychiatry and Neurology.

I wish to express my thanks to all my colleagues in the Laboratory. I gratefully ac-

knowledge Gabriella Juhász, Rita Jakus, Márton Graf, Eszter Kirilly, Rómeó Andó and

Judit Lazáry for their kindness, support and friendship at all times.

I am also indebted to Prof. Dr. Zoltán Rihmer for all his trust, support, encour-

agement and advice.

For their guidance and supervision and help in my research I express my thanks

to Prof. Dr. Péter Gaszner, Dr. András Lászik, Prof. Dr. Gábor Faludi, Dr. Zoltán Dan-

ics, Prof. Dr. Erika Szádóczky, Dr. Lilla Hárdi, and Dr. János Zámbori.

I would like to express my special thanks to my family and fiancée for their pa-

tience, love and encouragement, which was essential for the completion of my work.

Financial Support:

These studies were supported by the Sixth Framework Programme of the EU, LSHM-

CT-2004-503474, the Ministry of Welfare Research Grant 58/2003, the Hungarian Re-

search Fund Grants 022256/1997 and 032398/2000 and the PhD Fellowship Program of

the Semmelweis University, Ministry of Culture and Education, Hungary.

Documents

THE SEROTONIN TRANSPORTER GENE AND PERSONALITY: ASSOCIATION OF THE