Rumination in bipolar disorder: evidence for an unquiet mind

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].One of the earliest observations about bipolar depression is that it is more likely to be a melancholic depression. According to DSM-IV, the melancholic subtype is a depressed state characterized by anhedonia, excessive weight loss, psychomotor agitation or retardation, insomnia, worsening of symptoms in the morning, early morning awakening and excessive guilt. Although operational definitions of melancholia have varied over the years and across diagnostic systems (DSM III [10], DSMIII-R [11], Research Diagnostic Criteria [12], the World Health Organization Depression Scale [13], the Newcastle Scale - Versions I and II [13,14], Hamilton Depression Rating Scale [15]; see [16] for a review), the one consistent feature across the various definitions ha