Thursday, April 16, 2015
Prevalence of Bipolar I and II Disorder in Canada
There have only been two national surveys of mental health in Canada. One of these was conducted in 2002 (the CCHS 1.2) and a second one in 2012 (CCHS-MH). The first survey provided an estimate of bipolar disorder prevalence, see here. This prevalence was higher than expected, so a modified instrument that distinguished the two main types of Bipolar Disorder (I and II) in the 2012 survey. The prevalence has been revisited by Keltie McDonald, an MSc student in epidemiology at the University of Calgary. She found what seemed to be a more plausible prevalence, about 0.9% (traditionally, it has been believed that about 1% of the general population have Bipolar Disorder). However, there some very substantial inconsistencies also observed, e.g. few people with bipolar disorders were taking lithium, and few who reported that they had been diagnosed with Bipolar Disorder were detected by the version of the interview used in the survey. This paper raises some questions about the accuracy of research diagnostic interviews to accurately assess this condition. The result is not actually very surprising. The epidemiological diagnostic interviews used in this type of survey follow inflexible scripts and are well known not to perform well for all diagnoses. It is likely that the best way to study this condition will need to use data from other sources, such as anonymous, aggregate statistics from the health system, e.g. see another paper by Bulloch et al.