Cerebral ventricular size in twins discordant for schizophrenia.

Comparison of the computerised tomographic scans of 11 pairs of healthy monozygotic (MZ) with those of 8 pairs of dizygotic (DZ) twins showed that ventricular size for seven pairs of MZ twins discordant for schizophrenia was not as high as in normal MZ twins. Furthermore, the schizophrenics had significantly larger ventricles than both control twins and their own co-twins, although there was a non-significant trend for their co-twins also to have larger ventricles than the controls. Some common environmental factor, possibly perinatal damage, may have led to the increase in ventricular size in the schizophrenia-discordant pairs, with schizophrenia developing in the more severely affected twin.