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Physiology of mental illness

Physiology of mental illness. Schizophrenia Depression and mania Anxiety disorders. Schizophrenia. Broad set of symptoms Positive and negative symptoms Genetic factors in etiology 1% of general population 10% in first-degree relatives of probands 45% in identical twins of probands

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Physiology of mental illness

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  1. Physiology of mental illness Schizophrenia Depression and mania Anxiety disorders

  2. Schizophrenia • Broad set of symptoms • Positive and negative symptoms • Genetic factors in etiology • 1% of general population • 10% in first-degree relatives of probands • 45% in identical twins of probands • Same rate in children of probands (16.8%) as in children of their non-schizophrenic identical twins (17.4%) (Gottesman and Bertelsen, 1989)

  3. Etiological factors • Inherited susceptibility or several genes are involved • Retrospective strangeness in childhood behavior • Stress trigger • Dopamine hyperactivity is found in schizophrenia, but the genes for the five types of DA receptors found so far are not linked to schizophrenia (Coon et al., 1993)

  4. Environmental factors in etiology • We will see that dopamine hyperactivity relates to the positive symptoms of schizophrenia. • The negative symptoms may be due to brain damage: Some people with no family history of schizophrenia or any related disorder develop schizophrenia

  5. Prenatal damage factors: Epidemiology • Incidence of schizophrenia increases with: • season of birth: late winter/early spring • viral epidemics in second trimester • population density and latitude • malnutrition or refeeding after thiamine deficiency • prenatal stress

  6. More on brain damage • NADPH-d and cellular migration • Monochorionic monozygotic twins • More likely to be mirror-image twins • Monochorionic concordance: 60% • Dichorionic MZ concordance: 10.7% • DZ dichorionic concordance: 10% • Concordant MZ twins have nearly identical fingerprints and palm prints; non-concordant MZ twins do not.

  7. Evidence of brain damage in schizophrenia • Neurological symptoms • Catatonia and facial dyskinesias • Unusual rates of blinking, staring • Avoidance of eye contact • No blink reflex to a tap on the forehead • Stopped speech w/ looking away, esp. to right • Jerky eye movements and poor visual tracking • Interdependence of eye and head movements • Impaired reaction of pupils to light changes

  8. More evidence of brain damage • Structural symptoms • Doubling of size of lateral ventricles • Abnormalities in temporal and frontal lobes and in medial diencephalon • Smaller anterior hippocampus: smaller neurons • Decreased gray matter in left temporal lobe • Damage to left temporal lobe in adults may produce schizophrenia de novo • Low activity in prefrontal cortex (hypofrontality)

  9. Dopamine hypothesis • Hypofrontality lowers tonic release of DA in nucleus accumbens • Nucleus accumbens DA receptors become hypersensitive • Normal DA activity from VTA triggers positive symptoms of schizophrenia

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