for the Depression Screening Data (DEPRESSD) PHQ Collaboration IMPORTANCE The Patient Health Questionnaire depression module (PHQ-9) is a 9-item self-administered instrument used for detecting depression and assessing severity of depression. The Patient Health Questionnaire-2 (PHQ-2) consists of the first 2 items of the PHQ-9 (which assess the frequency of depressed mood and anhedonia) and can be used as a first step to identify patients for evaluation with the full PHQ-9.OBJECTIVE To estimate PHQ-2 accuracy alone and combined with the PHQ-9 for detecting major depression.

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/