Clustering of Unhealthy Diets, Inflammation Levels, and Depressive Symptoms in Chinese Adolescents: A Longitudinal Study

Abstract

Background/Objectives: Studies suggest a potential link between dietary behaviors, inflammation, and depressive symptoms in adolescents, but longitudinal evidence remains scarce. This study examines the longitudinal associations among unhealthy diets, inflammatory markers, and depressive symptoms in Chinese adolescents. Methods: This prospective longitudinal study enrolled 1693 middle school students (52.3% female) from Yunnan Province, China. Participants were assessed at five waves: October 2022 (T1), June 2023 (T2), October 2023 (T3), June 2024 (T4), and October 2024 (T5). Unhealthy dietary behaviors were assessed using a Food Frequency Questionnaire, and depressive symptoms were measured with the Children’s Depression Inventory. Blood samples were collected to measure inflammatory markers. Generalized estimating equations, generalized linear models, and path analysis were applied to examine the associations and mediating pathways. Results: Prevalence of depressive symptoms increased from 26.3% to 37.3% over 2 years. Compared with Q1 (the lowest quartile), Q4 of unhealthy dietary scores was significantly associated with an increased risk of positive depression symptoms (adjusted OR = 1.20). IL-4 (β =−0.26–−0.17) and CRP (β = 0.64–1.07) were associated with depressive symptoms. However, the mediating role of inflammation in the association between unhealthy dietary scores and depressive symptoms was not statistically significant. Conclusions: Chinese adolescents exhibit both a high clustering of unhealthy dietary behaviors and notably elevated levels of inflammation. Our longitudinal study indicates that the clustering of unhealthy diets and inflammation levels are associated with depressive symptoms among Chinese adolescents.