Background: There are few longitudinal studies investigating the risk of major depression by socioeconomic status (SES). In this study, data from the longitudinal cohort of Canadian National Population Health Survey were used to estimate the risk of major depressive episode (MDE) over 6 years by SES levels.
Methods: The National Population Health Survey used a nationally representative sample of the Canadian general population. In this analysis, participants (n=9589) were followed from 2000/2001 (baseline) to 2006/2007. MDE was assessed using the Composite International Diagnostic Interview--Short Form for Major Depression.
Results: Low education level (OR=1.86, 95% CI 1.28 to 2.69) and financial strain (OR=1.65, 95% CI 1.19 to 2.28) were associated with an increased risk of MDE in participants who worked in the past 12 months. In those who did not work in the past 12 months, participants with low education were at a lower risk of MDE (OR=0.43, 95% CI 0.25 to 0.76), compared with those with high education. Financial strain was not associated with MDE in participants who did not work. Working men who reported low household income (12.9%) and participants who did not work and reported low personal income (5.4%) had a higher incidence of MDE than others.
Conclusions: SES inequalities in the risk of MDE exist in the general population. However, the inequalities may depend on measures of SES, sex and employment status. These should be considered in interventions of reducing inequalities in MDE. MDE history is an important factor in studies examining inequalities in MDE.