evaluation of neural correlates

• the main issue is that it's unclear whether brain abnormalities are a causal factor in schiz or are due to having the disorder
• studies of the brain abnormalities are only performed after schiz has been diagnosed - longitudinal studies are needed that study the brain preceding schiz
• the issue of causality is highlighted by the fact that there are brain differences in the MZ twin pairs where only 1 twin has schiz - unlikely that the brain differences were present at brith
• another problem is that studies of the brain abnormalities in schiz do not always produce consistent results:

  Lewis (1990) examined 18 studies and found no significant link between enlarged ventricles and negative symptoms in schizophrenics, thus, reducing the support for the explanation