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How might genes contribute to a psychological disorder? How can we tell if a psychological disorder is influenced by genetics? Today’s session You will learn about Context Interpreting Schizophrenia biological data on the causes of mental illness The role of genetics and brain structure & processes in mental illness Schizophrenia: genetics Prevalence is the same all over the world (about 1%) Supports a biological view as prevalence does not vary with environm nmm ent However, there are variations within broad geographical areas (e.g. Torrey 2002 – Croatia & Ireland) Urbanicity data Schizophrenia: genetics Source: Gottesman (1991) Schizophrenia: genetics Risk rises with degree of genetic relatedness Spouse – 1% (same as G.P.) Child – 13% DZ twin – 17% MZ twin – 48% Effect of shared environment? Schizophrenia: genetics Adoption studies Prevalence amongst biological relatives Prevalence among adoptive relatives Kety et al (1968) schizophrenia only 13% 2% Tienari et al (1994) all ‘severe’ psych. diagnoses 30% 15% Schizophrenia: genetics Substantial evidence for a genetic contribution Some evidence disputed: Shared environment issues Diagnostic criteria in adoption studies All the evidence also suggests environmental trigger Where would a bio-psychologist start looking for the causes of schizophrenia (NB. be careful!)? What might they expect to find? Schizophrenia: brain Ventricular enlargement Schizophrenia: brain Cellular disarray Schizophrenia: brain Hypofrontality Schizophrenia: brain Grey matter loss (Thompson et al, 2001) Schizophrenia: brain Evidence for neurological changes in schizophrenia including: Loss of brain tissue Ventricular enlargement Cellular disarray Low activity in frontal areas Is schizophrenia a brain disease? Schizophrenia: brain No single abnormality common to all patients Some indication that abnormalities correlate with symptom types Confounding effect of drug treatments are a problem. Overlap with normal population Homework Evaluate the view that schizophrenia is a genetic disorder (at least a side of solid evaluative writing – use empirical evidence to support your argument). Briefly evaluate the view that schizophrenia is a brain disease (one substantial paragraph).