The prevalence of major depression is not changing.

Objective: To evaluate trends in the prevalence of major depressive episodes (MDEs) in Canada during the past 2 decades using data collected in a series of national surveys.

Method: MDE prevalence has been assessed in national surveys that either used a short form version of the Composite International Diagnostic Interview Short Form for Major Depression (CIDI-SFMD) or an adaptation of the World Health Organization's (full-length) version, World Mental Health (WMH) CIDI. We applied meta-regression methods to adjust for instrument type while also addressing design effects in the individual data sets. Interprovincial differences that might have confounded estimation of national trends were also explored.

Results: Interprovincial differences were not found to be significant, nor were time by province interactions. Estimates based on the WMH-CIDI were about 1% lower than those using the CIDI-SFMD. There was no evidence of changing prevalence over time, with slope for time, adjusted for assessment instrument, being nearly zero (β=0.0007, P=0.24).

Conclusion: An extensive collection of surveys conducted in Canada between 1994 and 2012 provide an opportunity to examine long-term trends in the prevalence of major depression. MDE prevalence has not changed during this period of time.