title: The 'true' prevalence of bipolar II disorder.
abstract: OBJECTIVE
  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.
  
  
  RESULTS
  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%.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Genetic Epidemiology Research Branch, Intramural Research Program, National Institutes of Health, National Institute of Mental Health, Bethesda, Maryland 20892-3720, USA. Kathleen.Merikangas@nih.gov
authors.forename: Kathleen R
authors.initials: KR
authors.lastname: Merikangas
authors.forename: Femke
authors.initials: F
authors.lastname: Lamers
mesh_terms: D001714:Bipolar Disorder / Q000145:classification / Q000453:epidemiology* / Q000523:psychology; D003072:Cognition Disorders / Q000523:psychology; D006801:Humans; D015994:Incidence; D015995:Prevalence