Morbidity risks of schizophrenia and affective disorders among first degree relatives of patients with schizophrenia, mania, depression and surgical conditions.

One thousand five hundred and seventy eight first degree relatives of schizophrenics, manics, depressives and controls were personally interviewed using the Iowa Structured Psychiatric Interview Form without knowledge of the probands' diagnoses. Our data, based on blind diagnostic assessment of the relatives, support the distinction between schizophrenia and affective disorders, although the distinction between schizophrenia and mania was not clear-cut. Our data could not support familial subtyping of paranoid and non-paranoid schizophrenia, and unipolar and bipolar affective disorders. Future studies attempting to develop research criteria for subtyping schizophrenia and effective disorders should utilize not only clinical and familial data but also biological markers and other non-familial variables.