Bipolar disorder with frequent mood episodes in the national comorbidity survey replication (NCS-R)
Virtually nothing is known about the epidemiology of rapid cycling bipolar disorder (BPD) in community samples. Nationally representative data are reported here for the prevalence and correlates of a surrogate measure of DSM-IV rapid cycling BPD from the National Comorbidity survey Replication (NCS-R), a national survey of the US household population. DSM-IV disorders were assessed in the NCS-R with the WHO Composite International Diagnostic Interview (CIDI). Although the CIDI did not assess rapid cycling, it did assess the broader category of 12-month BPD with frequent mood episodes (FMEs), having at least four episodes of mania/hypomania or major depression in the 12 months before interview. Roughly one-third of NCS-R respondents with lifetime DSM-IV BPD and half with 12-month BPD met criteria for FME. FME was associated with younger age-of-onset (of BP-I, but not BP-II) and higher annual persistence (73% of the years since first onset of illness with an episode) than non-FME BPD. No substantial associations of FME vs non-FME BPD were found with socio-demographics, childhood risk factors (parental mental disorders, other childhood adversities) or comorbid DSM-IV disorders. However, FME manic episodes had greater clinical severity than non-FME episodes (assessed with a fully structured version of the Young Mania Rating Scale) and FME hypomanic episodes had greater role impairment than non-FME episodes (assessed with the Sheehan Disability Scales). Whether these indicators of severity merely reflect attenuated effects of rapid cycling or independent effects of sub-threshold rapid cycling warrants further study given the high proportion of lifetime cases who met criteria for FME.