Major depression prevalence in Calgary

Objective: To estimate the 12-month period prevalence of major depression in Calgary. Methods: Subjects (n = 2542) were selected using random digit dialing (RDD) and interviewed by telephone using the Composite International Diagnostic Interview-Short Form for Major Depression (CIDI-SFMD). A subset of this sample was recontacted and administered the full mood disorders section of the CIDI. Results: The weighted proportion of the sample scoring in the positive range on the major depression predictor was 14.7%. Validation data determined that approximately three-quarters of these subjects would be expected to have major depression according to the CIDI. Hence, the estimated 12-month period prevalence of major depression was approximately 11.0%. Conclusions: This prevalence estimate is higher than most, but not all, previous Canadian estimates and resembles that of the American National Comorbidity Survey (NCS). Calgary may have high prevalence of major depression; however, because methodologically comparable studies are not available, to conclude this would be premature. Selection bias due to the RDD sampling (and the associated relatively high rate of nonresponse) may have led to an inflated prevalence estimate. Alternatively, because it allows increased anonymity and emotional "distance" from the nonprofessional interviews, telephone-based data collection may be more sensitive to psychopathology than face-to-face interviewing.