Mixed symptoms in major depressive and bipolar disorders: A systematic review

The DSM-5 mixed features specifier for mood disorders encourages renewed interest in mixed states and led us to pool research findings regarding prevalence of mixed features in episodes of major depressive (MDD) and bipolar disorders (BD).

We systematically searched to July 2017 for reports on mixed symptoms in depressive episodes of MDD and in depression and mania or hypomania in types I and II BD. For primary mood-states and diagnostic groups we compared rates of the presence of mixed symptoms: as defined by DSM-5 (≥3 features opposite to the dominant mood-polarity but not overlapping those of the primary disorder) or as having any ≥3 features of opposite polarity.

We identified 17 reports, from 13 world regions involving 19,198 participants meeting standard diagnostic criteria for an index major depressive or [hypo]manic episode. Prevalence of cases with ≥3 features of opposite polarity averaged 27.8% [CI: 27.2-28.5] overall, and differed significantly between BD and MDD disorders, ranking: BD-depressed (35.2% [33.8-36.5]) = BD-[hypo]manic (35.1% [32.9-37.3]) > MDD-depressed (23.8% [23.0-24.5]).

Available findings were limited to mood disorders with mixed features by particular criteria, with few comparisons to other criteria or to their prognostic or therapeutic implications.

Prevalence of ≥3 features of opposite polarity ranked: depressive = [hypo]manic episodes of BD > depression in MDD.