Activité physique et santé mentale chez les jeunes au collégial

Introduction Youth in transition to adulthood have lower levels of mental health compared to older adults, as well as the highest prevalence of anxiety and depression. There is growing interest in physical activity (PA) in mental health promotion and prevention. However, few studies examine the association between PA and mental health, partly due to the lack of reliable and valid measures of mental health in its positive sense. Further, how PA modalities and social mechanisms relate to mental health and mental disorders remains unclear. The objectives of this thesis were to 1) assess if the French-Canadian version of the Mental Health Continuum- Short Form (MHC-SF) is a reliable and valid measure of mental health; 2) examine the crosssectional associations between leisure-time PA volume and context and mental health, anxiety and depressive symptoms; 3) to determine if PA volume and social connectedness in PA are mediators of the association between PA context and mental health, anxiety and depressive symptoms. Methods A longitudinal study was conducted among post-secondary students in Quebec. A total of 1,527 participants completed an in-class questionnaire at baseline and 460 participated in the follow-up study 6 months later. Confirmatory factor analysis (CFA) was used to assess the factorial structure and sex-invariance of the MHC-SF. Internal consistency was assessed with Cronbach’s alpha and reliability was assessed with the rho reliability coefficient. Discriminant validity was examined against the Hospital Anxiety and Depression Scale (HADS) using Pearson correlation coefficients and CFA (Objective 1). Multivariate linear regressions were performed to model the associations between PA volume and context and mental health, anxiety and depressive symptoms (Objective 2). Mediation analyses were performed using causal inference methods based on counterfactuals. We estimated the controlled direct effect, natural direct and indirect effects with parametric models using the regression technique (Objective 3). Results The French-Canadian version of the MHC-SF is a valid and reliable brief self-report questionnaire that assesses mental health including three dimensions of well-being: emotional, social and psychological. Cross-sectional analyses indicated that higher PA volume and the team sport context are independently associated with higher mental health scores. Only higher moderate-to-vigorous PA volume was associated with lower levels of anxiety and depressive symptoms. Longitudinal analyses revealed that informal group and team sports contexts are associated with higher levels of mental health and lower levels of depressive symptoms, after controlling for covariates. Mediation analysis did not provide evidence suggesting that social connectedness in PA and PA volume are mediating variables of the association between PA context and mental health and depressive symptoms. Further research with larger samples and using social support, social belonging and social integration measures are needed to better elucidate the social mechanisms underlying the relationship between PA and mental health and mental disorders. Conclusion This study provides evidence of the reliability and validity of the French version of a mental health measure (MHC-SF). It also provides innovative empirical evidence of the importance of PA volume and social context to improve mental health and reduce mental disorders symptoms. Finally, the results of this thesis provide evidence for the development of interventions and public health guidelines for mental health promotion and prevention strategies for common mental disorders that rely on physical activity, among youth in transition to adulthood.

Keyphrases: Mental health, Anxiety, Depression, Physical activity, Informal group, Team sports, Relatedness to others, Youth, Causal inference and mediation analysis