Bipolar disorder is characterized b

Bipolar disorder is characterized by episodes of mania or hypomania, with or without one or more episode(s) of depression. By recent estimates, it affects between 1 and 2.5% of the general population in the United States [1]. Although mania/hypomania is the distinguishing feature of bipolar disorder, recurrent depressive episodes constitute the most frequent and functionally debilitating, unresolved aspect of the illness for individuals with bipolar disorder [2,3]. For example, over their lifetime, patients with bipolar disorder experience many more depressive episodes than manic or hypomanic episodes and spend longer amounts of time depressed than manic or hypomanic [4,5]. They are also more likely to consult a physician or psychiatrist for depression rather than for mania [6]. Likewise, depressive episodes are associated with comparatively greater occupational and psychosocial disruption then manic/hypomanic episodes. This includes impairments at work [6,7] as well as disruptions of patients' family and social life [6]. Unfortunately, despite the advancements in pharmacotherapy and the emergence of adjunctive psychosocial treatments, the diagnosis and management of bipolar depression remain significant challenges [8,9].