Research report The incidence of major depression in Canada: The National Population Health Survey JianLi Wang a,b, ⁎, Jeanne Williams b , Dina Lavorato b , Norbert Schmitz c , Carolyn Dewa d , Scott B. Patten a,b a Department of Psychiatry, Faculty of Medicine, University of Calgary, Canada b Department of Community Health Sciences, Faculty of Medicine, University of Calgary, Canada c Department of Psychiatry, McGill University, Canada d Department of Psychiatry, University of Toronto, Canada article info abstract Article history: Received 12 June 2009 Received in revised form 21 July 2009 Accepted 22 July 2009 Available online 31 August 2009 Objectives: To estimate the cumulative incidence of major depressive episode (MDE) over 6 years and the associations between demographic and socioeconomic variables and MDE in a sample of the Canadian national population. Methods: Data from the longitudinal cohort of the Canadian National Population Health Survey (NPHS) were used. MDE was assessed using the Composite International Diagnostic Interview — Short Form for Major Depression. Participants of the 2000/01 NPHS were followed until 2006/07. Individuals with previous MDE were excluded from the analysis. Proportional hazard models were developed to assess the associations between demographic, socioeconomic characteristics and MDE. Results: The cumulative incidence of MDE at 2002/03, 2004/05 and 2006/07 was 2.9% (95% confidence interval: 2.3%, 3.4%), 5.7% (95% confidence interval: 4.9%, 6.4%) and 7.2% (95% confidence interval: 6.4%, 8.1%). Women, youth, participants with one or more chronic medical conditions and those who reported family history of MDE were more likely to have developed MDE. Family history was the strongest risk factor for MDE (hazard ratio=2.01, 95% confidence interval: 1.51, 2.68). Conclusion: It may be valuable for primary and secondary prevention efforts to target women and young people. Family history is an important factor which should be considered in epidemiological studies about major depression, and also can assist in identifying those at high risk of new-onset MDE. © 2009 Elsevier B.V. All rights reserved. Keywords: NPHS Major depression Incidence Family history Population-based Cohort 1. Introduction The Global Disease Burden (GDB) study sponsored by the World Health Organization and World Bank reported that, of the ten leading causes of disease burden worldwide in 1990s, unipolar depression or major depression ranked number four (Murray and Lopez, 1996). In 2001, major depression ranked number three in the GDB study in terms of disease burden (Lopez et al., 2006). Major depression is prevalent in the general population. In Canada, based on the data from the Canadian Community Health Survey — Mental Health & Wellbeing (the first Canadian national mental health survey), the annual prevalence of major depressive episode was 4.8% (Patten et al., 2006). In the United States, the 12-month prevalence of major depressive disorder was 6.6% (Kessler et al., 2003). Prevalence is a parameter of the disease burden. Whereas incidence quantifies new cases of disease and Journal of Affective Disorders 123 (2010) 158–163 ⁎ Corresponding author. Room 127, Heritage Medical Research Building, 3330 Hospital Dr. NW, Calgary, AB, Canada T2N 4N1. Tel.: +1 403 210 8653; fax: +1 403 210 8802. E-mail address: jlwang@ucalgary.ca (J. Wang). 0165-0327/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.jad.2009.07.016 Contents lists available at ScienceDirect Journal of Affective Disorders journal homepage: www.elsevier.com/locate/jad