• We examined the sex ratios of unipolar and bipolar affective disorder in 14 studies of bipolar illness. The data are highly consistent in demonstrating that (1) females are more frequently affected than males; (2) among affected females, the ratio of unipolar depression to bipolar illness is about 2:1; whereas (3) among affected males, the ratio of bipolar to unipolar illness is approximately 1:1. This curious discrepancy between the sexes may hold a clue to understanding familial transmission as well as heterogeneity in bipolar illness.
Winokur G, Crowe RR. Bipolar IllnessThe Sex-Polarity Effect in Affectively Ill Family Members. Arch Gen Psychiatry. 1983;40(1):57-58. doi:10.1001/archpsyc.1983.01790010059007