Schizophrenia: sex and familial morbidity.

Several recent studies have found a greater risk of schizophrenia among the relatives of female schizophrenic probands than the relatives of male schizophrenic probands. These results are contradictory to those of earlier studies. The current investigation, using family data collected in the 1950's and 1960's in Sweden, did not find a difference in the risk of schizophrenia among the relatives of male and female schizophrenic probands. However, significantly more relatives of female probands than relatives of male probands had manic-depressive psychosis. These findings suggest that the earlier studies may have included some female schizophrenic probands who would be classified as having manic-depression by modern criteria.