Prevalence of Bipolar I and II Disorder in Canada

Current epidemiologic knowledge about bipolar disorder (BD) in Canada is inadequate. To date, only 3 prevalence studies have been conducted: only 1 was based on a national sample, and none distinguished between BD I and II. The objective of this study was to estimate the prevalence of BD I and II in Canada in 2012.

Data were obtained from the 2012 Canadian Community Health Survey: Mental Health and Well-being, a cross-sectional survey of a nationally representative sample of household residents ages 15 years and older (n = 25 113). The survey response rate was 68.9%. Interviews were based on the World Health Organization Composite International Diagnostic Interview (CIDI). Prevalence was estimated using generalized linear modelling. Prevalence of self-reported diagnosis of BD and use of lithium were also estimated.

The estimated lifetime prevalence of BD I and II (based on the CIDI) in Canada in 2012 was 0.87% (95% CI 0.67% to 1.07%) and 0.57% (95% CI 0.44% to 0.71%), respectively. Prevalence did not differ by sex. The estimated prevalence of self-reported BD was 0.87% (95% CI 0.65% to 1.07%). There was a lack of congruence between CIDI-defined and self-reported BD, and few people taking lithium were positive for BD on the CIDI, which raises some concerns about the validity of the CIDI's assessment of BD.

These prevalence estimates align with those reported in prior literature. However, caution should be exercised when interpreting general population studies that use CIDI-defined BD owing to the possibility of misclassification.