Overview

Abstract (English)

The Global Burden of Disease project reported that mental disorders have accounted for at least 14% of years of life lost due to disability since 1990. Common mental disorders—such as major depressive disorder and anxiety disorders—rank highly among the major causes of disease burden; globally, they are estimated to be associated with at least 12 billion days of lost productivity per year, costing approximately $925 billion USD. Given their high morbidity and societal cost, concerns exist that the prevalence of these common mental disorders have been increasing in developed countries over the past 30 years. Evidence supporting these concerns is uncertain, in part because there has not been significant epidemiologic surveillance that has applied consistent measures of morbidity continuously over a long duration in population-based samples. Surveillance in Germany among those aged 18 to 79, and in Canada among those aged 12 and older observed stable depression prevalence measured over a ten-year period ending in 2012. In contrast, a United States surveillance report noted a slight increase in depression among those aged 12 and older between 2005 and 2015. A meta-analytic synthesis of primarily European general population samples showed no increase in anxiety disorders from 1990 to 2010. However, in Australia, general population samples from the National Survey of Mental Health and Wellbeing showed an increase in anxiety symptoms among adults older than age 18 from 1997 to 2007. Part of the reason for the uncertainty in general population samples is that these samples may mask trends in higher-risk subgroups. Unemployment or not being in the labour force is associated with a higher risk of mental illness, yet few studies have taken this into account in longitudinal prevalence estimates. Given the changes in workplaces, job markets, and macroeconomic conditions that have impacted labour forces over the past two decades, there is a need for surveillance that explores the impact of microeconomic and macroeconomic conditions on prevalence trends among various labour force groups at the population level. This evidence can be used by researchers, economists, employers and policy makers to manage the burden of mental disorders on labour markets. Optimal characteristics for these surveillance systems include continuity of measurement over time, consistency of measurement over time, population-based sampling, and reliability in the measurement of health status and health risks. Although these criteria are particularly salient for monitoring prevalence trends of common mental disorders at the population level, they have limitations in currently available evidence. This study aims to address these gaps by examining prevalence in a high-income country by implementing a repeated cross-sectional study design to estimate trends in the prevalence of depression and anxiety disorders in representative samples of working-age Canadian adults over a 17-year period.

Abstract (French)

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