Revisiting depressive-prone bipolar disorder: polarity of initial mood episode and disease course among bipolar I systematic treatment enhancement program for bipolar disorder participants.

Background: We examined the hypothesis that a first depressive rather than manic episode in bipolar disorder might herald a subsequent course notable for greater burden of depressive symptoms.

Methods: We analyzed retrospective data on the polarity of first mood episode obtained from 704 bipolar I subjects entering the multicenter Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD) study. Subjects with an initial manic or depressive episode and those in whom both poles occurred within the same year were compared.

Results: Depressive-onset bipolar disorder was more common in women and those with earlier onset of illness. Adjusting for these differences, it was significantly associated with more lifetime depressive episodes and a greater proportion of time with depression and anxiety in the year prior to study entry.

Conclusions: Polarity of first mood episode may be useful in distinguishing subsets of bipolar patients at risk for a more chronic course.