Mixed states in bipolar II disorder: should full hypomania always be required?

The aim of the study was to test whether the definition of depressive mixed states (DMX) in bipolar II disorder should require satisfaction of full criteria for hypomania or if only a few hypomanic symptoms should be required. Consecutive outpatients with bipolar II major depressive episode (MDE) (n=260) were assessed with the Structured Clinical Interview for DSM-IV. Presence of hypomanic symptoms during MDE was systematically assessed, and symptoms were graded by rating scale. The following three definitions of DMX were compared: (1) MDE plus full criteria for hypomania, (2) MDE plus three or more hypomanic symptoms (DMX3), and (3) MDE plus one or two hypomanic symptoms (DMX1-2). DMX definitions were compared on variables typically associated with bipolar disorders (young age of onset, many recurrences, atypical features of depression, and bipolar family history). The distributions of hypomanic symptom scores, age, and age of onset were studied by Kernel density estimation curves and by histograms. Bimodality would support distinct disorders, whereas lack of bimodality would support continuity among the different DMX definitions. The frequency of DMX+full hypomania was 12.3%, that of DMX3 was 46.9%, and that of of DMX1-2 was 38.8%. Comparisons among the groups on bipolar validators found that most differences were not significant. Kernel density estimation curves and histograms did not show bimodality, and had near normal distribution shapes. The findings do not support a categorical definition of bipolar II DMX like that of DSM-IV for bipolar I mixed state but are consistent with a dimensional definition of bipolar II DMX. The high frequency of DMX in bipolar II MDE supports the need for controlled studies to test the effects of antidepressants on depressive mixed state (as clinical observations suggest possible negative effects).