Longitudinal Associations between Dietary Intake and Common Mental Disorders among Adolescents in Australia

Background: There is need for more longitudinal research exploring temporal associations between diet quality and common mental disorders (CMDs) during adolescence. This study examined prospective associations between indicators of adolescents’ diet quality (fruit, vegetable and sugar-sweetened beverage [SSB] intakes) and risk of depression and anxiety onset, over three years. We hypothesised higher fruit and vegetable intake, and lower SSB intake, would be associated with lower risk of CMDs. Method: This study included 6537 Australian adolescents (mean age 12.65 years at baseline). Students completed surveys at baseline, 1-, 2-, and 3-year follow-ups. We fitted Generalised Estimating Equations Poisson regression models to assess longitudinal associations between daily serves of fruit, vegetables, and SSBs, and risk of depression and anxiety onset (binary cut-points on validated scales) over 3 years. Models were re-run for males and females. Analyses excluded participants who met thresholds for depression or anxiety at baseline, to increase confidence that diet predicted onset of CMDs. Results: Adolescents with heathier diet indicators (higher fruit and vegetable, lower SSB intakes) had lower risk of developing depression. The same was true for associations between both fruit and SSB (but not vegetable) intake and anxiety. Subgroup analyses revealed sex differences for associations between healthy indicators (fruit, vegetables) and CMDs, but higher SSB intake was associated with higher CMD risk for both sexes. Results inform the Global burden of disease Lifestyle And mental Disorders project (DERR2-10.2196/65576). Conclusions: Longitudinal research exposing temporal associations between diet and CMDs may inform prevention/intervention efforts targeting modifiable risk factors for CMDs.