The authors report their comparison of socioenvironmental, familial, and genetic characteristics in matched groups of bipolar (manic-depressive) and unipolar patients. While affective illness was present in a majority of the families of both groups, bipolar illness appeared only in the families of bipolar patients, suggesting a familial or genetic source for this disease. Parental deprivation and marital failure rates were significantly higher in the bipolar group.Abstract Teaser