The association of physical activity, sleep, and screen time with mental health in Canadian adolescents during the COVID-19 pandemic: A longitudinal isotemporal substitution analysis.

Background: The impact of COVID-19 on adolescent mental health is a global concern. Increased screen time and reduced physical activity due to the lockdown measures have been linked to detrimental mental health outcomes; however, the literature remains limited by cross-sectional and retrospective designs, and consideration of behaviours in isolation. Prospective evidence is necessary to examine whether moderate-to-vigorous physical activity (MVPA), sleep and screen time influenced changes in mental health.

Changes in Canadian Adolescent Time Use and Movement Guidelines During the Early COVID-19 Outbreak: A Longitudinal Prospective Natural Experiment Design.

Background: Comprehensive, prospective, longitudinal data are lacking on the effects of the COVID-19 outbreak on adolescents' movement behaviors (moderate to vigorous physical activity [MVPA], sleep, recreational screen use, and strengthening exercises). The purpose was to compare movement behavior changes among adolescents affected by the pandemic with controls.

Methods: Survey data from 10,659 students at 82 Canadian secondary schools (aged 12-19 y) during the 2018-2019 and 2019-2020 school years were analyzed.

Alcohol, marijuana, and tobacco use patterns among youth in Canada.

The authors characterized changes in the prevalence of alcohol, tobacco, and marijuana use over time, and examined age of onset, co-morbid use and sociodemographic factors associated with ever using alcohol, tobacco, or marijuana in a nationally representative sample of Canadian youth. Data were collected from students in grades 7-9 as part of the Canadian Youth Smoking Survey (n = 19,018 in 2002; n = 29,243 in 2004). Descriptive analyses examined age of onset, co-morbid substance use and changes over time.