Symptoms of major depressive disorder during the COVID-19 pandemic: results from a representative sample of the Canadian population

INTRODUCTION: Since the outbreak of COVID-19, numerous studies from around the world have reported declines in mental health. However, most of these studies were of low-to-moderate quality and many were based on convenience samples or used mental health measures with low validity, or both. Consequently, it has been difficult to draw conclusions. METHODS: Both the 2020 Survey on COVID-19 and Mental Health (SCMH) and the Canadian Community Health Survey (CCHS) (2015-2019) used the Patient Health Questionnaire-9 to screen for major depressive disorder (MDD) in adults aged 18 or older. The prevalence of MDD was compared between the SCMH and the CCHS. Risk and protective factors for MDD in the SCMH were examined using bivariate and logistic regression analyses. RESULTS: Based on SCMH data, 15.2% (95% CI: 14.2-16.2) of Canadians screened positive for MDD. The prevalence of MDD was more than two times higher in the SCMH (during COVID-19) than in the CCHS (predating COVID-19). In bivariate analysis, Canadians reporting five or more COVID-19-related risk factors were close to 30 times more likely to have MDD than those reporting no risk factors. Mastery and a sense of community belonging were protective factors for MDD. CONCLUSION: After remaining stable for two decades, the prevalence of depression among Canadians increased substantially with the onset of COVID-19. Ongoing monitoring of this common condition associated with major morbidity is vital to determine if elevated levels of MDD persist as we progress through and beyond future waves of COVID-19.