More inclusive bipolar mixed depression definitions by requiring fewer non-overlapping mood elevation symptoms

Assess strengths and limitations of mixed bipolar depression definitions made more inclusive than that of the Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5) by requiring fewer than three 'non-overlapping' mood elevation symptoms (NOMES).

Among bipolar disorder (BD) out-patients assessed with Systematic Treatment Enhancement Program for BD (STEP-BD) Affective Disorders Evaluation, we assessed prevalence, demographics, and clinical correlates of mixed vs. pure depression, using less inclusive (≥3 NOMES, DSM-5), more inclusive (≥2 NOMES), and most inclusive (≥1 NOMES) definitions.

Among 153 depressed BD, compared to less inclusive DSM-5 threshold, our more and most inclusive thresholds, yielded approximately two- and five-fold higher mixed depression rates (7.2%, 15.0%, and 34.6% respectively), and important statistically significant clinical correlates for mixed compared to pure depression (e.g. more lifetime anxiety disorder comorbidity, more current irritability), which were not significant using the DSM-5 threshold.

Further studies assessing strengths and limitations of more inclusive mixed depression definitions are warranted, including assessing the extent to which enhanced statistical power vs. other factors contributes to more vs. less inclusive mixed bipolar depression thresholds having more statistically significant clinical correlates, and whether 'overlapping' mood elevation symptoms should be counted.