Schizophrenia Week 2Psychology with BCS1 The Dopamine Hypothesis The dopamine hypothesis: Schizophrenia is caused by excessive Dopamine (DA) activity. This causes abnormal functioning of the parts of the brain which use DA, resulting in schizophrenic symptoms

Schizophrenia Week 2Psychology with BCS2 In CA, from 1955 to 1980, institutionalized population declined from to 2 500

Schizophrenia Week 2Psychology with BCS3 The Dopamine Hypothesis S symptoms can be treated with DA antagonists (eg. chlorpromazine). These are effective in 60% of cases with more impact on positive symptoms. AO2: Supports role of DA again, but what about 40% who don’t respond? AO2: Lack of impact on negative symptoms hints at two separate syndromes AO2: Despite fact that antipsychotics work on blocking D2 receptors right away, there is a delay in the relief of symptoms

Schizophrenia Week 2Psychology with BCS4 The Dopamine Hypothesis Wise & Stein (1973) report abnormally low levels of DBH in post-mortem studies of S patients Would suggest abnormally high DA activity as DBH needed to break DA down AO2: Can’t rule out cause of death or post- mortem changes as a source or error

Schizophrenia Week 2Psychology with BCS5 The Dopamine Hypothesis Taking lots of amphetamine (a DA agonist*) can produce S-like symptoms. S patients have abnormally large responses to low amphetamine doses Suggests a role for DA in S symptoms Suggests that the issue is over- sensitivity to DA rather than excessive DA levels (*an agonist refers to a compound that stimulates or enhances activity of the DA receptors)

Schizophrenia Week 2Psychology with BCS6 The Dopamine Hypothesis A major metabolite of dopamine (HVA) has not been found in greater amounts in patients with schizophrenia. Schizophrenics may have more dopamine receptors, not dopamine in brain. AO2: post-mortems on schizophrenics show their brains have more dopamine receptors than aged-matched controls, and PET Scans have confirmed this.

Schizophrenia Week 2Psychology with BCS7 The Dopamine Hypothesis AO2: Consistent evidence that neurochemical factors cause abnormal brain functioning in S patients but no single factor identified AO2: Cause and Effect – does elevated DA activity cause S or is it simply the effect? AO2: Newer drugs (eg. Clozapine) also target serotonin receptors and reduce negative symptoms as well as positive AO2: Treatment-Aetiology Fallacy

Schizophrenia Week 2Psychology with BCS8 Mortensen et al. (1999)

Schizophrenia Week 2Psychology with BCS9 Mortensen et al. (1999)