High frequency of bipolar spectrum in outpatients with depression.

The frequency of bipolar II disorder (BD II) is higher than the 0.5% community prevalence reported in DSM-IV-TR (1): rates are 11% in the community (2,3) and 30% to 60% in outpatients suffering from depression (4,5). Diagnostic criteria for “bipolar spectrum disorder” (6) include major depressive episode (MDE), no spontaneous mania or hypomania, family history of BD, and (or) antidepressantinduced mania or hypomania, plus some of the following: hyperthymic personality, many MDEs, short-duration MDEs, atypical and psychotic features, young and postpartum onset, short-duration antidepressant response, and no response to many antidepressants. The diagnosis of depressive mixed state (DMX), defined as MDE plus 3 or more concurrent hypomanic symptoms, has received clinical, family history, and psychometric validation (7–9) and replication (10,11). DMX is common in patients with BD II (up to 60%) and in MDE outpatients with major depressive disorder (MDD) (up to 30%). Links between MDD with DMX and BD II have been found (specifically, similar age of onset, atypical features, and bipolar family history) (7), supporting its inclusion in the bipolar spectrum (4,5). The current study aimed to determine the frequency of the bipolar spectrum in outpatients with depression, including bipolar spectrum disorder, MDD with DMX, and BD II.