The association between diet and mental health and wellbeing in young adults within a biopsychosocial framework

Objective: Predominantly plant-based diets can co-benefit human physical health and the planet. Young adults appear to be on the forefront of the shift to plant-based diets. However, little is known about the relationship between plant-based diets and mental health in this population even though mental health disorders contribute substantially to the global burden of disease, particularly among this age group. Design: In this cross-sectional study we utilize a biopsychosocial framework to assess the association between dietary intake and mental health and wellbeing. Mental health was assessed using self-reported measures of anxiety (GAD-7), depression (PHQ-9) and quality of life (single-item). Dietary intake in the prior month was assessed using a dietary screener (DSQ) and participants were asked to self-identify a diet preference (e.g., vegan). Setting and participants: 339 university undergraduate students. Results: A principal component analysis of dietary intake found three dominant dietary patterns (plant-based, animal-based, and ‘junk foods’); 28.1% (n = 95) of participants self-identified as pescatarian, vegetarian, vegan, other. The association between dietary patterns, diet preference and mental health was assessed through regression analysis. After controlling for covariables, we found a significant positive association between the junk food component and depression (z-score β = .21, p≤.001; adj. R2 = .39) and anxiety (z-score β = .14; p≤.001; adj. R2 = .32) while no association was found between plant-based, animal-based or self-identified diet preference and the mental health measures. Conclusions: We did not find a negative association between predominantly plant-based diet patterns and mental health and wellbeing. It is important to consider dietary composition and to conceptualize diet as a health behaviour that is embedded in a biopsychosocial framework.