Prevalence and correlates of bipolar II disorder in major depressive patients at a psychiatric outpatient clinic in Hong Kong

BackgroundWestern studies indicate a high prevalence of bipolar II disorder defined by a Research Diagnostic Criteria 2-day hypomania duration criterion (30 to 61%) amongst clinically depressive patients. The situation in Chinese patients with depression is unknown.Methods64 (52.5% response rate) patients first presenting to a Hong Kong public psychiatric outpatient clinic in 2005 with a diagnosis of major depression were recruited. The SCID and Family History Screen were administered.ResultsDSM-IV bipolar II was found in 20.5% of depressive outpatients; 35.9% had bipolar II disorder defined by RDC 2-day duration criterion for hypomania. Family bipolarity, age of onset, and depressive recurrence distinguished bipolar II subjects from unipolar depressives irrespective of duration criteria chosen for hypomania.LimitationsSample size was limited.ConclusionsBipolar II disorder is common amongst Chinese depressive outpatients. The evaluation method and 2-day duration criterion for hypomania were supported by bipolar validators. Replication using larger samples is needed to arrive at a more representative prevalence estimate and to enable more refined nosological evaluation.