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 <12 at the same visit, was observed in 2,139 visits (14.9% of total visits, and 43.5% of visits with depression) by 584 patients (64.4% of all patients). Women were significantly more likely than men to experience subthreshold hypomania during visits with depression (40.7% compared with 34.4%). Patients with one or more mixed depression visits had more symptomatic visits and fewer euthymic visits compared with those with no mixed depression visits. DSM-5-based definitions of mixed depression (ranging from narrower definitions requiring ≥3 nonoverlapping 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.