Family history and schizophrenia: characteristics of groups with and without positive family histories.

Social and demographic characteristics were examined retrospectively in a sample of 475 hospitalized schizophrenics to test the hypothesis that they can be meaningfully distinguished by the presence or absence of psychiatric disorders in their relatives. Cases with a positive family history of psychiatric disorders (FHP cases) were significantly more likely to have been born in the United Kingdom and to have had older mothers. Those who had relatives with psychiatric disorders other than schizophrenia were significantly more likely to have been diagnosed as schizo-affective. The findings are thought to reflect a constitutional trait in parents of FHP cases leading to delayed child bearing. They also support the 'environmental stress' theory of immigrant psychosis and the hypothesized genetic link between schizo-affective and affective disorders.