ental health disorders, including major depressive disorder, are classified in research using validated diagnostic interviews. 1,2 However, administering diagnostic interviews to large population samples to estimate prevalence is expensive because of the time and trained personnel that are required. This is likely why researchers increasingly use selfreport screening questionnaires, which require fewer resources, to estimate prevalence. We searched PubMed from Jan. 1, 2017, to Mar. 14, 2017, for primary studies with titles that indicated that prevalence of depression or depressive disorders had been assessed. Prevalence was based on screening questionnaires in 17 of 19 studies (89%; Appendix 1, available at www.cmaj.ca/ lookup/suppl/