Bipolar disorder--focus on bipolar II disorder and mixed depression.

Bipolar II disorder (recurrent depressive and hypomanic episodes) and related disorders (united in the bipolar spectrum) are understudied, despite a prevalence of about 5% in the community and about 50% in depressed outpatients. The apparent increase in prevalence of the bipolar spectrum is related to several changes in diagnostic criteria, including improved probing for history of hypomania (focused more on overactivity than on mood change), lower minimum duration of hypomania, and inclusion of unipolar depressions with bipolar signs (eg, family history of bipolar disorder, mixed depression). Prevalence of mixed depression, a combination of depression and manic or hypomanic symptoms, is high in patients with bipolar disorders. Controlled studies are needed to investigate treatment of mixed depression; antidepressants can worsen manic and hypomanic symptoms, and mood stabilising agents might be necessary.