Evidence for homogeneity of major depression and bipolar affective disorder.

This study compared the morbidity risk for affective disorder in relatives of probands who had bipolar (BP) or major depression (UP). Other risk factors were also evaluated. 112 consecutively admitted inpatients yielded 621 relatives with diagnostic information based on either the Renard diagnostic interview, hospital records or information from at least two reliable relatives using the Feighner diagnostic criteria. Similar age corrected morbid risk estimates were found for family members of UP and BP probands of 0.243 and 0.246. There was a 50% increase in morbidity risk for women in all three generations but no relationship to the diagnosis of the proband. A proportional hazards (life table) analysis demonstrated that probands with onset prior to age 40 had relatives with younger onset and higher risk. None of the analyses, including logistic regression and proportional hazards, differentiated UP from BP illness.