Healthy bodies, healthy minds? The behavioural and social determinants of mental health in Australian adolescents and outcomes of the Health4Life cluster randomised controlled trial

Abstract

The global prevalence of mental disorders has increased in recent decades, particularly amongst adolescents and young adults. Behavioural determinants (including diet, physical activity, sleep, screen time, alcohol use, and tobacco use) and social determinants (including gender, culture, and socioeconomic status) are two areas that offer important considerations for the prevention of adolescent mental disorders. However, there are several key gaps in extant literature.

First, few studies consider both behavioural and social determinants in the one adolescent cohort. Second, few studies consider the relationship between behaviour change and adolescent mental health. Third, there is a gap for Australian data, despite the heightened burden of disease attributable to mental disorders in Australia. Finally, no studies have examined behavioural intention and mental health outcomes of school-based interventions that target diet, physical activity, sleep, screen time, alcohol use, and tobacco use.

This thesis addresses these knowledge gaps and builds the evidence base around the role of behavioural and social determinants of mental health among adolescents. It provides evidence that can guide policymakers, practitioners, schools, and adolescents themselves in the quest to stem the increasing prevalence of mental disorders in adolescents.

This thesis has several standout findings. It demonstrates: 1) that addressing adolescent lifestyle behaviours offers promise for preventing adolescent mental ill-health, 2) the need to address the gender gap for both lifestyle behaviour-change and mental health, and 3) the potential of the Health4Life universal school-based intervention to improve behavioural intentions and mental health. It ends by offering practical suggestions for policymakers, schools, adolescents, and researchers to implement, aiming to ensure that this timely research is translated to enhance adolescent mental health in Australia and beyond.