The relationship between dietary nutrient intake and adolescent depression based on the dietary inflammation index: a case-control study

Abstract Background and purpose The global increase in adolescent Major Depressive Disorder (MDD) has profound implications for physical and mental development, contributing to a significant societal burden. Emerging evidence suggests that low-grade chronic inflammation, commonly observed in adolescents with MDD, is associated with the severity of the disorder. This study explores the relationship among dietary inflammation, dietary nutrients and adolescent depression, utilizing data from the Energy-adjusted Dietary Inflammatory Index (E-DII) in a population from northern China. Methods A case-control study was conducted between March 2022 and October 2023, involving 172 treatment-naïve adolescents aged 10–23 years diagnosed with MDD and 172 age- and sex-matched healthy controls. Although the calculated minimum sample size was 174 per group, two matched pairs were excluded during data cleaning because extreme dietary reporting could have biased nutrient intake estimation. The E-DII was derived using data from a validated semi-quantitative Chinese food frequency questionnaire (FFQ). Logistic regression was employed to evaluate the association between E-DII and the risk of adolescent MDD, while restricted cubic spline (RCS) functions assessed the dose-response relationships between specific dietary nutrient intakes and MDD. Results A positive association was identified between the E-DII and the risk of adolescent MDD (OR = 3.24; 95% CI: 2.32–4.51; P < 0.001), which persisted after adjusting for potential confounders (OR = 3.23; 95% CI: 2.22–4.69; P < 0.001). Although an increase in E-DII score correlated with higher HAMD scores, intra-group differences were not statistically significant ( P = 0.159). Several dietary nutrients, including Vitamin B12, dietary fiber, zinc, polyunsaturated fatty acids (PUFA), folate, and anthocyanins, were negatively associated with the risk of MDD in adolescents, whereas carbohydrates, selenium, and alcohol intake were positively associated with MDD risk (all P < 0.05). RCS analysis showed nonlinear dose–response relationships for PUFA, anthocyanins, vitamin B12, and alcohol intake, whereas selenium, zinc, folate, carbohydrates, and dietary fiber showed linear associations with MDD risk. Conclusion This study underscores a positive correlation between the E-DII and both the risk and severity of adolescent depression, emphasizing the critical role of dietary factors in the prevention and management of adolescent depression. From a clinical and public health perspective, early dietary assessment and promotion of anti-inflammatory dietary patterns may provide a feasible adjunctive strategy for reducing depression risk in adolescents.