Chapter 16 Schizophrenia and Affective Disorders

Chapter 16

Schizophrenia and Affective Disorders

Schizophrenia Description

Schizophrenia:• A serious mental disorder characterized by:

Disordered thoughts

Delusions of persecution or grandeur

Hallucinations (mostly auditory)

Behaviors (withdrawn or detached, odd movements))

Schizophrenia Description

Positive symptom: (known by their presence)• delusions, hallucinations, abnormal movements,

or thought disorders.

Negative symptom: (characterized by absence)• social withdrawal, lack of affect, and reduced

motivation.

Schizophrenia

Possible Causes:• Heritability: In its simplest form, if schizophrenia was

determined by a single dominant gene, about 75% of children from schizophrenic parents would get it. If it was recessive, about 50% would inherit the disorder. An incidence less than 50% suggests that the disease is determined by multiple genes and that only a susceptibility is passed on.

Schizophrenia

Evidence for heritability• Concordance rates:

Most studies suggest between 25-40% in identical twins and about 5-20% in fraternal twins.

Clearly, the environment is an important contribution.

Schizophrenia

Biochemical Causes• Dopamine Hypothesis: schizophrenia is caused

by excessive dopamine activity in the mesolimbic system.

• Supporting evidence: drug treatment, amphetamine psychosis, treatment for Parkinson’s disease

• Additional evidence: increased DA activity, increased D3 & D4 receptors in mesolimbic system,

Schizophrenia Pharmacology of Schizophrenia

Chlorpromazine: A phenothiazine• A “typical neuroleptic”; a nonspecific dopamine

receptor blocker; first prescribed antischizophrenic drug.

Clozapine:• An “atypical neuroleptic”; an antipsychotic drug

that blocks D4 receptors in the nucleus accumbens. Little effect on D2 receptors

Copyright © 2004 Allyn and Bacon


Schizophrenia Consequences of Long-Term Drug Treatment of

Schizophrenia

Tardive dyskinesia:• A movement disorder that can occur after

prolonged treatment with antipsychotic medication, characterized by involuntary movements of the face and neck.

Supersensitivity:• The increased sensitivity of neurotransmitter

receptors; caused by damage to the afferent axons or long-term blockage of neurotransmitter release.

Schizophrenia

Evidence for neurological abnormalities Negative symptoms

Schizophrenics with negative symptoms have similar symptoms as those with fromtal lobe damage.• Frontal lobe size• Ventrical size • Cerebral gray matter decreases



Schizophrenia Possible Causes of the Brain Abnormalities

Epidemiology:• The study of the distribution and causes of

diseases in populations.

• Research suggest several environmental factors:-Season of birth: greatest during winter months-Viral epidemics: associated with viral diseases-Latitude: increased incidence further from equator-Prenatal malnutrition: ?-Rh incompatibility: ?-Maternal stress: ?





Major Affective Disorders Description

Major affective disorders:• A serious mood disorder; includes major

depressive disorder and bipolar disorder.

• May effect as many as 5% of US population in a given year. Perhaps as many as 25% over lifetime.

Major Affective Disorders Description

Major depressive disorder:• A serious mood disorder that consists of

unremitting depression or periods of depression that do not alternate with periods of mania.

Bipolar disorder:• A serious mood disorder characterized by

cyclical periods of mania and depression.

Major Affective Disorders Causes of Depression Genetic contributions:

• Bipolar disorder may be caused by a single dominant gene.Location still not confirmed, but heritability studies reveal strong link.

Major depressive disorder:• Less likely caused by single gene than bipolar

disorder.• Amine hypothesis: deficiencies in activity of one

or several amine neurotransmitter systems (NE, SE)

Major Affective Disorders Drug Treatment for Depression

Tricyclic antidepressants:• A class of drugs used to treat depression; inhibits the

reuptake of norepinephrine and serotonin; named for the specific molecular structure.Amitriptyline (Elavil)

Monoamine oxidase inhibitors (MAOIs):• Prevent degradation of NT in synapse.

phenelzine (Nardil) Serotonin specific reuptake inhibitor (SSRI):

• A drug that inhibits the reuptake of serotonin without affecting the reuptake of other neurotransmitters.

fluoxetine (Prozac)

Major Affective Disorders Physiological Treatments

Lithium• A chemical element; lithium carbonate is used to

treat bipolar disorder Carbamazepine:

• An anticonvulsive drug (trade name: Tegretol) that is used to treat seizures originating from a focus, also used to treat mania in bipolar disorder.


Major Affective Disorders Physiological Treatments

Electroconvulsive therapy (ECT):• A brief electrical shock that induces a seizure;

used therapeutically to alleviate severe depression when medication is not effective.

Transcranial Magnetic Stimulation (TMS):

Magnetic field causes a weak electrical field and electrical current within the brain. Has been useful in some cases of depression.


Major Affective Disorders Evidence of Brain Abnormalities

Brain abnormalities:• Research suggests abnormalities in the

prefrontal cortex, basal ganglia, hippocampus, thalamus, cerebellum, and temporal lobes.

• Some evidence suggests increased size of the cerebral ventricles may suggest the loss of neural tissue.

Major Affective Disorders Evidence of Brain Abnormalities

Silent cerebral infarction (SCI):• A small cerebrovascular accident (stroke) that

causes minor brain damage without producing obvious neurological symptoms.

Major Affective Disorders Role of Circadian Rhythms

REM Sleep Deprivation:• Selective deprivation of REM sleep through EEG

monitoring, is one of the most effective antidepressant treatments; suggests a close relationship between REM sleep and mood.

• Antidepressant effects require several weeks of deprivation.




Major Affective Disorders Role of Circadian Rhythms

Total Sleep Deprivation:• Total sleep deprivation has antidepressant effect

that are immediate; however, the procedure is not very practical.

• Some individuals do not respond to total or selective sleep deprivation.

Major Affective Disorders Role of Zeitgebers

Seasonal affective disorder (SAD):• A mood disorder characterized by depression,

lethargy, sleep disturbances, and craving for carbohydrates during the winter months.

Summer depression:• A mood disorder characterized by depression,

sleep disturbances, and loss of appetite.

Major Affective Disorders Role of Zeitgebers

Phototherapy:• Treatment of seasonal affective disorder by daily

exposure to bright light.

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Chapter 16 Schizophrenia and Affective Disorders