Youth diet quality and hazard of mood disorder in adolescence and adulthood among an Australian cohort

Background Prospective studies on youth diet and mood disorders outcomes are limited. We examined if youth diet quality was associated with mood disorder onset over a 25-year follow-up period. Methods In 1985, Australian participants (aged 10–15 years) completed a 24-hour food record. A validated 100-point Dietary Guidelines Index (DGI) assessed diet quality. In 2009–11, 1005 participants (aged 33–41 years) completed the lifetime Composite International Diagnostic Interview for age of first DSM-IV defined mood disorder (depression or dysthymia). Cox proportional hazards regression estimated hazard of mood disorder during the 25-year follow-up according to baseline DGI score. Sensitivity analyses censored the study at 5, 10, and 15 years after baseline and used log binomial regression to estimate relative risk (RR). Covariates included baseline negative affect, BMI, academic performance, smoking, breakfast eating, physical activity, and socioeconomic status. Results The mean(SD) youth DGI score was 45.0(11.5). A 10-point higher DGI was not associated with hazard of mood disorder onset over the 25-year follow-up (Hazard Ratio (HR):1.00; 95% Confidence Interval (CI):0.89–1.13). The only indication that higher DGI might be associated with lower risk of mood disorder was within the first 5 years after baseline and this was not statistically significant (RR=0.85; 95% CI:0.60–1.18). Limitations Loss-to-follow-up. A single 24-hour food record may not represent usual diet. Conclusion Youth diet did not predict mood disorders in adulthood. The suggestions of a lower risk of mood disorder during late adolescence highlights that further prospective studies are needed