Article Sections

Introduction

Bipolar II disorder is a chronic mood disorder that involves ≥1 hypomanic episode and ≥1 major depressive episode with no history of mania.  Hypomanic episodes are characterized by ≥4 days of elevated, expansive, or irritable mood and persistently increased energy.  "Bipolar" refers to the 2 poles of mania/hypomania and depression; in bipolar II disorder, patients fluctuate between hypomania and depression or experience these two mood states simultaneously (ie, episode with mixed features).  Recurrent alternating mood states and depressive episodes result in significant functional impairment and often require lifetime maintenance treatment.

Epidemiology and risk factors

The lifetime prevalence of bipolar II disorder is estimated to be 0.4% among adults.  Prevalence rates are similar in men and women, and the average age at onset is the mid-20s.

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