Supplemental Material for COVID-19 Pandemic Mental Health Trajectories: Patterns From a Sample of Canadians Primarily Recruited From Alberta and Ontario

Public Significance Statement Public health responses to the pandemic coronavirus disease (COVID-19) could adversely impact the mental health of Canadians. Understanding changes in Canadian mental health during the pandemic and the factors that confer risk and resilience could guide future pandemic public health policies. During the first 6 months of the COVID-19 pandemic, Canadians experienced changes in depressive and anxiety symptoms that paralleled COVID-19 infection rates and Health Canada pandemic response recommendations. Coronavirus disease (COVID-19) is a highly contagious and novel virus that has prompted government officials to implement restrictive public health orders. It is hypothesized that pandemic-related restrictions may have a detrimental impact on mental health. Longitudinal data were collected through 13 assessments, repeated every 2 weeks for the initial 6 months of the COVID-19 pandemic. Participants were recruited through [Masked] University and social media. The final sample consisted of 280 adults from across Canada, with the majority of participants residing in Alberta (63%) and Ontario (20%). Sociodemographic characteristics, COVID-19 related risk factors, prepandemic and pandemic physical activity, and COVID-19 related risk factors were collected at study entry, and mental health (depressive symptoms, anxiety, and loneliness) were collected at each assessment. Multilevel modeling was used to identify mental health trajectories during the initial 6 months of the pandemic. Mental health symptoms tracked with rising cases of infection and subsequent public health restrictions during the pandemic. Specifically, anxiety and depressive symptoms demonstrated strong longitudinal quadratic trends. Both anxiety and depressive symptoms were high at study entry (May 2020) and decreased over the summer, followed by an increase in the fall and winter months. Loneliness was stable over the follow-up period. Age, sex, living alone, socioeconomic factors, and preexisting mental health conditions correlated with mental health symptoms during the pandemic's initial 6 months. This study characterizes within-person changes to mental health (anxiety, depressive symptoms, and loneliness) in a Canadian sample from May 2020 to January 2021 during the COVID-19 pandemic.