Twin studies - Joseph - concordance rate of 40.4% in MZ, 7.4% in DZ
Adoption studies - Tienari - bio mothers with SZ - 6.7% in children, 2% without bio mother
Candidate gene studies
Early research looked for a single, SZ-causing gene
SZ is polygenic and aetiologically heterogeneous
Ripke et al. - compiled genome-wide studies, found 108 genes associated with SZ risk
Benzel et al. - COMT, RDR4, AKT genes cause excess dopamine, leading to positive symptoms
Miyakawa et al. - DNA from families with SZ, those with more likely to have a defective PPP3CC gene
The Dopamine Hypothesis
V1 - Schizophrenia is caused by excess dopamine activity in the brain, particularly the mesolimbic pathway. This was based on the effects of dopamine-blocking antipsychotics and dopamine-releasing drugs
V2 - Updated hypothesis added low levels of DA in the prefrontal cortex, which may explain negative symptoms
Davis et al. - frontal hyperdopaminergia in rats, frontal lobe lesions and negative symptom correlation
Neural correlates
Patterns of activity in the brain that occur in conjunction with an experience, and may be the cause of the experience
