title: Estimated prevalence of the seasonal subtype of major depression in a Canadian community sample.
abstract: OBJECTIVE
  To examine estimates of lifetime prevalence of seasonal affective disorder (SAD) in Toronto, Ontario.
  
  
  METHODS
  Random telephone numbers were generated for the city of Toronto, and 781 respondents completed a telephone interview. Trained nonphysician interviewers conducted all interviews, which involved structured questions for diagnosing major depression. Patterns of symptom change across seasons were evaluated to establish a diagnosis of SAD according to DSM-III-R criteria.
  
  
  RESULTS
  Correcting for sex and age, the prevalence of SAD defined by DSM-III-R criteria was 2.9% (95% CI, 1.7% to 4.0%), and the overall lifetime prevalence of major depression in the sample was 26.4% (95% CI, 23.3% to 29.4%). Some subjects were contacted for a follow-up interview conducted in person; the positive predictive value for the diagnosis of major depression for the telephone interview was 100%, and the negative predictive value was 93%.
  
  
  CONCLUSIONS
  The seasonal subtype of depression represents 11% of all subjects with major depression, suggesting that SAD is a significant public health concern. The telephone interview demonstrated adequate reliability, indicating that it is appropriate for epidemiological surveys of this nature.
authors.affiliation: University of Toronto, Department of Psychiatry. anthony.levitt@swchsc.on.ca
authors.forename: A J
authors.initials: AJ
authors.lastname: Levitt
authors.forename: M H
authors.initials: MH
authors.lastname: Boyle
authors.forename: R T
authors.initials: RT
authors.lastname: Joffe
authors.forename: Z
authors.initials: Z
authors.lastname: Baumal
mesh_terms: D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003865:Major Depressive Disorder / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D016574:Seasonal Affective Disorder / Q000175:diagnosis / Q000453:epidemiology* / Q000523:psychology; D014505:Urban Population / Q000706:statistics & numerical data*