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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Behaviors (withdrawn or detached, odd movements))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
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
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
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: ?
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
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.
Copyright © 2004 Allyn and Bacon
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.
Copyright © 2004 Allyn and Bacon
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.
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
Copyright © 2004 Allyn and Bacon
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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