The genetics of depression. A family study of unipolar and neurotic-reactive depressed patients.

Sixty unipolar (23 male and 37 female) patients and 67 patients (25 male and 42 female) suffering from a neurotic-reactive depressive disorder, consecutively admitted to the Department of Psychiatry of Umeå University have participated in a family study aimed at identifying morbidity risks for psychiatric illnesses among first degree relatives (n = 437). Besides the classification of affective disorders used in Umeå for research purposes the patients have been classified, according to the ICD-9, DSM-III, age at onset (below or above 40 years), and the Winokur's classification of primary affective disorders. However, only the findings regarding the Umeå classification and the Winokur's classification are given in the present article. Of the patients 90% fulfilled Kendell's criteria for depression at the time of the investigation whereas the others were in a phase of remission when studied. The diagnosis of secondary cases were made without knowledge of the diagnoses of the probands. Among relatives of unipolar probands only two secondary cases of bipolar affective disorder were found--one among parents, and one among siblings (MR% 1.1 and 0.6 respectively). The overall morbidity risk for affective disorders (MR% 22.8 among parents and 15.5 among siblings) proved to be higher than in previous studies. In the families of neurotic-reactive patients the morbidity risk for bipolar affective disorders was also very low (MR% 1.0 among parents and 0.7 among siblings), whereas the overall MR% for affective disorders proved to be surprisingly high (12.1 among parents and 6.7 among siblings). No increased risk for schizophrenia or alcoholism was found among the relatives of either group. When the relatives were divided according to their sex no clear-cut difference in morbidity risk emerged when fathers and brothers were compared with mothers and sisters but alcoholisms occurred more frequently in male relatives. Preliminary findings in second degree relatives suggest that secondary cases of affective disorders might occur among second degree relatives of patients classified as suffering from "sporadic depression" according to Winokur's classification.