Objectives: To review the current knowledge of bipolar II disorder.
Methods: Literature was reviewed after conducting a Medline search and a hand search of relevant literature.
Results: Bipolar II disorder is a common disorder, with a prevalence of approximately 3–5%. Distinct clinical features of bipolar II disorder have been described. The key to diagnosis is the recognition of past hypomania, while depression is the typical presenting feature of the illness. This is responsible for a significant rate of missed diagnosis, and consequent management according to unipolar guidelines. It is unclear if bipolar II disorder is over-represented amongst resistant depression populations and if abrupt offset of antidepressant action is a phenomenon over represented in bipolar II disorder, reflecting induction of predominantly depressive cycling. A few mood-stabilizer studies available provide provisional suggestion of utility. A supportive role for psychosocial therapies is suggested, however, there is a sparsity of published studies specific to bipolar II disorder cohorts. A small number of short-term antidepressant trials have suggested efficacy, however, compelling long-term maintenance data is absent.
Conclusions: An emerging literature on the specific clinical signature and management of the disorder exists, however, this is disproportionately small relative to the epidemiology and clinical significance of the disorder.