Biological explanations for schizophrenia

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Twin Studies

Gottesman- summarised 40 studies and found a 48% concordance rate for MZ twins and 17% for DZ twins but only 1% for the general population

Rosenthal- case study of quadruplets all developed schizophrenia with variation of onset and symptoms

Cardono- 26.5% concordance rate for MZ twins and 0% for DZ twins


-small sample sizes

-McGuffin et al- different diagnostic criteria was used so we can't compare

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Adoption Studies

Aattempts to separate nurture/nature factors

Kety- reccorded high rates of schizophrenia in individuals whose biological parents had it; even though they were adopted by healthy parents

Tianari- 155 finnish adopted children whose mothers had schizophrenia; 10% also developed schizophrenia compared to 1% of the control group who had no family history of schizophrenia

but this study had methodological issues and lacks validity

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Dopamine Hypothesis

Schizophrenia is the result of an excess of dopamine at synaptic sites

Evidence for this can be found in

Phenothiazines- block dopamine at receptors and work in aliviating symptoms of schizophrenia- but not for everyone

L-dopa- used to treat parkinsons by increasing dopamine- but it produces schizophrenia symptoms

Wong et al- PET scans found increased dopamine receptor density in non drug treated schizophrenia patients

However Farde et al could not replicate these results in later studies

reductionist to assume it is purely dopamine

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Buchsbaum found reduced blood flow in central lobes and some symptoms of schizphrenia have been known to arise from this area

Szesco- schizophrenia patients have unusual symmetry in their brain

Crow- the two syndrome hypothesis-

Type 1 schizophrenia- a genetic acute onsetting type that responds well to medication

Type 2 schizophrenia- a neuroanatomical chronic type that doesnt respond well to medication

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