Objective: Adolescence frequently coincides with the onset of psychiatric illness, and depression is commonly observed in adolescents. Recent data suggest an increase in rates of psychological distress in young people over recent decades, whilst nutrition surveys concurrently suggest that the quality of adolescents’ diets has decreased over a similar time-period. This study measured the extent to which diet quality was related to depression in adolescents.

Methods: The study examined 7114 adolescents, aged 10-14 years, who participated in the Australian Healthy Neighbourhoods Study. Healthy and unhealthy diet quality scores were derived from food frequency data. The Short Mood and Feelings Questionnaire for adolescents measured depression. Adjustments were made for age, gender, socioeconomic status, father's education, mother’s education, father's work status, family conflict, poor family management, dieting behaviours, physical activity, and smoking.

Results: Compared to the lowest category of the healthy diet score, the odds ratios (95% confidence interval) for symptomatic depression across categories (C) was: C2 = 0.61 (0.45-0.84); C3 = 0.58 (0.43-0.79); C4= 0.47 (0.35-0.64); and C5= 0.55 (0.40-0.77). Compared to the lowest quintile, the odds ratios (95% confidence interval) for symptomatic depression across increasing quintiles of the unhealthy diet score were: Q2 =1.03 (0.87-1.22); Q3 = 1.22 (1.03-1.44); Q4 = 1.29 (1.12-1.50); and Q5 = 1.79 (1.52-2.11).

Conclusions: Our results demonstrate dose-response associations between diet quality and adolescent depression that exist over and above the influence of socioeconomic, family, and other potential confounding factors.