A controlled family study of chronic psychoses. Schizophrenia and schizoaffective disorder.

Two hundred thirty-seven relatives of 48 patients with chronic psychosis, diagnosed as either schizophrenia or schizoaffective disorder, along with 380 relatives of psychiatrically normal controls, were studied using systematic diagnostic interviews, information from relatives, and review of medical records where appropriate. A variety of nonbipolar psychotic disorders was found in the relatives of the patients. Comparing relatives of patients with schizophrenia with relatives of patients with schizoaffective disorder, there was no tendency for schizoaffective diagnosis or acute psychoses to aggregate separately from schizophrenia. Increased incidence of bipolar disorder was found in relatives of patients with schizoaffective disorder but not in relatives of patients with schizophrenia. Incidence of major affective disorder (bipolar and unipolar) was increased in relatives of probands with both types of psychoses. If we subdivide the ill probands according to whether or not they had a history of substance abuse, relatives of probands with substance abuse had greater frequency of affective disorder and substance abuse, but there were not significant differences in the number of relatives with nonbipolar psychoses.