Mixed Depression in Bipolar Disorder: Prevalence Rate and Clinical Correlates During Naturalistic Follow-Up in the Stanley Bipolar Network

Objective: DSM-5 introduced the "with mixed features" specifier for major depressive episodes. The authors assessed the prevalence and phenomenology of mixed depression among bipolar disorder patients and qualitatively compared a range of diagnostic thresholds for mixed depression.

Method: In a naturalistic study, 907 adult outpatients with bipolar disorder participating in the Stanley Foundation Bipolar Network were followed longitudinally across 14,310 visits from 1995 to 2002. The Inventory of Depressive Symptomatology-Clinician-Rated Version (IDS-C) and the Young Mania Rating Scale (YMRS) were administered at each visit.

Results: Mixed depression, defined as an IDS-C score >= 15 and a YMRS score >2 and = 3 non overlapping YMRS items concurrent with an IDS-C score >= 15 to broader definitions requiring >= 2 nonoverlapping YMRS items) yielded lower mixed depression prevalence rates (6.3% and 10.8% of visits, respectively) but were found to have similar relationships to gender and longitudinal symptom severity.

Conclusions: Among outpatients with bipolar disorder, concurrent hypomanic symptoms observed during visits with depression were common, particularly in women. The DSM-5 diagnostic criteria for depression with mixed features may yield inadequate sensitivity to detect patients with mixed depression.