The 'true' prevalence of bipolar II disorder

Many studies - including meta-analyses - do not distinguish between bipolar I and II disorder. The aim of this study is to review the recent literature on the prevalence, correlates, consequences, and treatment patterns of bipolar II disorder.

In the past 2 years, several important studies have been conducted in the bipolar II field. The World Mental Health Survey initiative provides us with prevalence rate across 11 countries, while several meta-analyses on suicide and neurocognition directly compared bipolar I with bipolar II, informing us on the severe consequences of bipolar II disorder. Results from studies showed that the lifetime prevalence rate of bipolar II disorder in adults across 11 countries was 0.4%. Rates of bipolar II disorder in prospective studies of adolescents are substantially greater, with lifetime rates approaching 3-4%.

Evidence from these studies regarding comparable clinical consequences, patterns of comorbidity, suicide attempts, family history, and treatment patterns to bipolar I disorder document the validity of the bipolar II subtype.