The impact of the COVID-19 pandemic on adolescent mental health is a global concern; however, most research is cross-sectional or started after the pandemic response began and thus unable to evaluate within-individual change. The purpose of this prospective study was to evaluate the effect of the initial COVID-19 response on adolescent mental health and ill-health as a natural experiment. We used 3-year linked data from the COMPASS study, including 7,653 Canadian (Quebec, Ontario) adolescents from which 2,099 completed surveys in all three waves (pre-COVID-19 [2018 and 2019] and online [May–July 2020], 2–3 months into the pandemic). A structural equation modeling approach to fixed effects and a difference-in-differences design were used to estimate pre-COVID-19–to–early lockdown change in mental health (psychosocial well-being [flourishing—reverse scored]) and ill-health (depression and anxiety symptoms), compared with 2018-to-2019 change. Models were adjusted for self-selection, age of entry into the cohort, and sociodemographics. Depression, anxiety, and reverse-flourishing scores increased across all waves; however, the mental health changes from the pre-COVID-19 wave (2019) to 2020 were not greater relative to the changes seen across the 2018-to-2019 waves. Our results do not support a detrimental effect of the initial stages of the COVID-19 lockdown measures on adolescent mental health. The deterioration in mental health in the early COVID-19 response was less than the decline found over a prepandemic period. Further prospective research is needed to explore the impact of the prolonged pandemic and related measures on adolescents and inequitable effects in population subgroups.

Our aim was to examine measurement invariance of the Flourishing Scale (FS)—a concise measure of psychological wellbeing—across two study samples and by population characteristics among Canadian adolescents. Data were retrieved from 74,501 Canadian secondary school students in Year 7 (2018–2019) of the COMPASS Study and from the original validation of the FS (n = 689). We assessed measurement invariance using a confirmatory factor analysis in which increasingly stringent equality constraints were specified for model parameters between the following groups: study sample (i.e., adolescents vs. adults), gender, grade, and ethno-racial identity. In all models, full measurement invariance of the FS across all sub-groups was demonstrated. Our findings support the validity of the FS for measuring psychological wellbeing among Canadian adolescents in secondary school. Observed differences in FS score among subgroups therefore represent true differences in wellbeing rather than artifacts of differential interpretation.

Background: There remains a need for prospective research examining movement behaviours in the prevention and management of mental illness. This study examined whether changes in adherence to the 24-h Movement Guidelines (moderate-to-vigorous physical activity [MVPA], sleep duration, screen time) were associated with depression symptoms among youth.Methods: Conditional change models were used to analyze two waves of longitudinal questionnaire data (2016/17, 2017/18) from students in grades 9–12 (N = 2292) attending 12 schools in Ontario and British Columbia, Canada, as part of the COMPASS study. One-year change in adherence to the MVPA, screen time, and sleep duration guidelines were modeled as predictors of depressive symptoms, adjusting for covariates and prior year depressive symptoms. Models were stratified by sex.Results: Continued adherence to sleep guidelines and transitioning from inadequate to sufficient sleep were associated with lower depressive symptoms than continued nonadherence, and continued adherence was associated with lower depression than transitioning from sufficient to short sleep. For screen time, transitioning from exceeding guidelines to guideline adherence was associated with lower depressive symptoms than continued nonadherence. MVPA guideline adherence was not associated with depression scores, when controlling for sleep and screen time guideline adherence change and covariates. When combined, meeting additional guidelines than the year prior was associated with lower depressive symptoms among females only.Conclusions: Adherence to the sleep guidelines emerged as the most consistent predictor of depression symptoms. Promoting adherence to the Movement Guidelines, particularly sleep, should be considered priorities for youth mental health at a population level.

Background: The purpose of this study was to explore whether the way youth perceive their weight and their experiences of bullying victimization account for the increased risk of depression and anxiety symptoms, and poor psychosocial well-being, associated with overweight/obesity in a large sample of Canadian secondary school students. We also explored if associations differed by gender. Methods: We used cross-sectional survey data from year 7 (2018–19) of the COMPASS study. The sample included 57,059 students in grades 9–12 (Secondary III-V in Quebec) at 134 Canadian secondary schools (Alberta, British Columbia, Ontario, Quebec). First, multiple regression models tested associations between body mass index (BMI) classification and mental health outcomes (anxiety [GAD-7] and depression [CESD-10] symptoms, and psychosocial well-being [Diener’s Flourishing Scale]). Second, weight perception and bullying victimization were added to the models. Models were stratified by gender and controlled for sociodemographic covariates and school clustering. Results: When weight perception and bullying victimization were added to the models, obesity BMI status no longer predicted internalizing symptoms and flourishing scores relative to normal-weight BMIs. Students with ‘overweight’ or ‘underweight’ perceptions, and experiences of bullying victimization in the past month, reported higher anxiety and depressive symptomatology, and lower flourishing levels, in comparison to students with ‘about right’ weight perceptions and without experiences of bullying victimization, respectively, controlling for BMI status. Results were largely consistent across boys and girls. Conclusions: Results suggest perceptions of weight and experiences of bullying independently contribute to differences in mental health outcomes by weight status among youth. Continued efforts targeting weight-based bullying and weight bias, and the promotion of body size acceptance and positive body image, may help reduce the risk of mental illness and poor mental health among adolescents.