Healthier diets to promote mental health in adolescents: building the evidence.
Creators: Dabravolskaj, Julia
Publisher: name: University of Alberta Library
Year: 2023

<p>Background: Unhealthy diet is a well-established risk factor for developing many physical health conditions in adolescents (e.g., obesity, type 2 diabetes). Evidence begins to emerge that unhealthy diet might also be implicated in the development of common mental disorders. While there is a plethora of high-quality prospective studies on the association between diet and mental disorders in adults, such studies in adolescents are scarce. The already high and rising burden of mental disorders in adolescents necessitates a careful examination of diet as a potential target for interventions to improve mental health in adolescents. The overarching goal of this dissertation was to estimate the effect of diet (alone and in combination with other lifestyle behaviours, including substance use behaviours) on mental health in Canadian middle adolescents (i.e., 14-17 years old). <br>
Methods: The goal has been achieved in a series of four interconnected research papers that utilized data from the Cannabis, Obesity, Mental health, Physical activity, Alcohol, Smoking, and Sedentary behaviour (COMPASS) study – a large longitudinal study which annually collects survey data from ~60,000 grade 9 to 12 high school students in British Columbia, Alberta, and Ontario, and Secondary I-V students in Quebec. <br>
Results: The systematic review in Chapter 2 revealed several methodological concerns in existing studies: i.e., inadequate adjustment for established confounders and unnecessary adjustment for intermediate variables, and the need for sensitivity and sex-based subgroup analyses. Studies identified in this evidence synthesis, along with those identified in another ongoing systematic review (PROSPERO CRD42021246478), informed a list of covariates that likely confound the diet-mental health association in adolescents: i.e., mental health at baseline, socio-economic status, age, eating behaviours, lifestyle behaviours (i.e., physical activity, sedentary behaviours, sleep, and substance use behaviours, including tobacco smoking, vaping, cannabis and alcohol use), and social support. Analyses in a sample of 13,887 COMPASS study participants (Chapter 3) were adjusted for this set of confounders. Analyses revealed a small negative effect of sugar-sweetened beverages (SSB) consumption on depressive and anxiety symptoms, as well as a small positive effect of vegetables and fruit consumption on psychological wellbeing. In Chapter 4, the focus was on dietary trajectories in vegetables and fruit and SSB consumption in relation to depressive and anxiety symptoms in a prospective cohort panel of 5,653 COMPASS participants who provided their responses in three consecutive waves of data collection. Analyses showed that the consumption of VF and SSB changed for the worse over time, and that the rate at which these changes happen was associated with the severity of depressive symptoms (but not anxiety symptoms). Finally, in Chapter 5, a holistic approach was taken to account for the synergistic effect that a comprehensive range of co-occurring unhealthy lifestyle behaviours might have on mental health. Indeed, when considered in combination, meeting more recommendations was generally associated with lower severity of depressive and anxiety symptoms at one-year follow-up. <br>
Conclusion: The results of this thesis highlight the need for dietary interventions (particularly those implemented at the policy level, such as taxation of SSBs, banning food marketing to children, and subsidizing healthy foods to low-income families, among others) as part of comprehensive population-level primary prevention strategies, which target other lifestyle behaviours as well, to improve mental health in adolescents.</p>