Bipolar disorder with frequent mood episodes in the New Zealand Mental Health Survey

Background Rapid cycling bipolar disorder has been studied almost exclusively in clinical samples. Methods A national cross-sectional survey in 2003–2004 in New Zealand used the Composite International Diagnostic Interview (CIDI 3.0). Diagnosis was by DSM-IV. Depression severity was assessed with the Quick Inventory of Depressive Symptoms (QIDS) and role impairment using Sheehan Scales. Complex survey analyses compared percentages and means, and used logistic regression and discrete-time survival analyses. Frequent mood episodes (FMEs) in the past 12 months (4+) were used as an indicator of rapid cycling. Results The lifetime prevalence of bipolar disorder (I + II) was 1.7%. Twelve-month prevalence was 1.0%: 0.3% with FME and 0.7% with No FME (1–3 episodes). Another 0.7% had no episodes in that period. Age of onset was earliest for FME (16.0 years versus 19.5 and 20.1, p < .05). In the past 12 months, weeks in episode, total days out of role and role impairment in the worst month were all worse for the FME group (p < .0001) but both the FME and No-FME groups experienced severe and impairing depression. Lifetime suicidal behaviours and comorbidity were high in all three bipolar groups but differed little between them. About three-quarters had ever received treatment but only half with twelve-month disorder made treatment contact. Limitations Recall, not observation of episodes. Conclusions Even in the community the burden of bipolar disorder is high. Frequent mood episodes in bipolar disorder are associated with still more disruption of life than less frequent episodes. Treatment is underutilized and could moderate the distress and impairment experienced.