Gender differences in bipolar disorder: retrospective data from the first 500 STEP-BD participants

OBJECTIVE: To examine gender differences in a large sample of patients with bipolar illness. METHODS: Exploratory analysis of baseline data from the first 500 patients in the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD), a multi-center NIMH project. Participants are allowed to have medical and psychiatric comorbidities, and to enter in any mood state, thus making the population more generalizable than many research cohorts. Diagnoses and history were assessed using structured clinical instruments administered by certified investigators. Given the exploratory nature of these analyses, there is no correction of for multiple comparisons. However, we emphasize findings that are statistically significant at the more stringent p < 0.01 level. RESULTS: Compared with men, women had higher rates of BPII (15.3% M versus 29.0% F, p < 0.01), comorbid thyroid disease (5.7% M versus 26.9% F, p < 0.01), bulimia (1.5% M versus 11.6% F, p < .0.01) and post-traumatic stress disorder (10.6% M versus 20.9% F, p < 0.01). Women and men had equal rates of history of lifetime rapid cycling and depressive episodes. Men were more likely to have a history of legal problems (36% M versus 17.5% F, p < 0.01). CONCLUSIONS: Potentially important gender differences in certain illness characteristics were found in our study; however, in contrast to other reports, we did not find higher rates of lifetime depressive episodes or rapid cycling in women. Although our study is limited by its retrospective study design, its results are strengthened by our large sample size and use of structured interviews.