Mixed depression is distinct from the DSM mixed episode in that it is conceptualized primarily as a depressive episode. Recently, we characterized prevalence of mixed hypomania (Suppes et al., 2005). This study replicates that methodology, examining the prevalence of mixed depression in this large cohort.

Patients (n=908) enrolled in the Stanley Foundation Bipolar Network were assessed monthly (14,328 visits) on manic (YMRS) and depression symptoms (IDS-C). To minimize the overlap between these two measures, a modification (IDS-Mod), which excluded items captured on the YMRS, was developed (Suppes et al., 2005). Mixed depression was defined as significant depressive symptoms (IDS-Mod>=12, equivalent to IDS-C>=15) and subthreshold manic symptoms (YMRS > 3 and < 12).

Of the total visits, 11.7% met criteria for mixed depression. Of the patients, 57.9% reported at least one visit meeting these criteria. Mixed depression was more common in women (64%) vs. men (53%, χ2(1df)=8.6, p<.01). A history of anxiety disorders and alcohol/ substance use disorders was associated with a higher percentage of patients reporting a mixed depressive visit [history of anxiety disorder = 79% vs no anxiety disorder = 57%, χ2(1df)=25.05, p<.01; history of alcohol /substance use disorders = 69% vs. no substance use disorder = 58%, (χ2(1DF)=8.15, p<01)].

Many bipolar patients experience depressive symptoms with hypomanic symptoms. These data suggest this is more prevalent in women vs. men and when anxiety or substance use disorders are in the clinical history. Further analyses are warranted to assess the predictive implication of co-occurring symptoms.