A family study of DSM-III-R schizoaffective disorder, depressive type, compared with schizophrenia and psychotic and nonpsychotic major depression.

OBJECTIVE: To assess the validity of DSM-III-R schizoaffective disorder, the authors explored the morbid risks for schizophrenia and major affective disorders in the first-degree relatives of patients with schizoaffective disorder and relevant other diagnoses.
METHOD: In addition to patients with DSM-III-R schizoaffective disorder, depressive type (N = 21), the probands included patients with mood-incongruent psychotic depression (N = 22), mood-congruent psychotic depression (N = 19), nonpsychotic depression (N = 27), or schizophrenia (N = 28) and normal subjects (N = 18). The patients were consecutively recruited from the outpatient facilities of a university psychiatry department; the normal subjects were students and nurses. All probands were directly interviewed, with the Schedule for Affective Disorders and Schizophrenia--Lifetime Version (SADS-L), by a psychiatrist blind to information about relatives. Consenting relatives were directly interviewed, with the SADS-L, by two psychiatrists blind to the probands' diagnoses. The direct interview was supplemented--or replaced, when an interview was not possible (24%)--by family history data from all available sources. Morbid risks in relatives were calculated according to the Weinberg method.
RESULTS: The relatives of the schizoaffective patients had almost the same risk for schizophrenia as the relatives of the schizophrenic patients. In the relatives of the patients mood-incongruent psychotic depression, the morbid risk for major affective disorders was about one-half that of the relatives of the patients with mood-congruent psychotic depression and one-third that of the relatives of the patients with nonpsychotic depression, but these differences did not reach statistical significance.
CONCLUSIONS: These results suggest that DSM-III-R schizoaffective disorder is close to schizophrenia and largely corresponds to mainly schizophrenic schizoaffective disorder in the Research Diagnostic Criteria, whereas DSM-III-R mood-incongruent psychotic depression is probably quite heterogeneous and should be studied further.