Impact of Outdoor Environmental Exposome on Depressive Symptoms Among Children Aged 9-14 in China

To assess associations between multiple environmental factors and depressive symptoms (DS) among children and adolescents, we conducted a school-based longitudinal study among 1,418 Chinese students aged 9-14 years, with baseline and follow-up surveys conducted from 2022 to 2023. Twenty outdoor environmental exposures from three domains, air pollutants, meteorological conditions, and geographical features were assessed. DS was measured using the Center for Epidemiologic Studies Depression Scale. An exposome-wide association study was used to explore associations and identify important environmental exposures related to DS, followed by eXtreme Gradient Boosting to rank their relative importance. Composite scores for three environmental domains were constructed to assess their joint impacts on DS. Exposure to PM_2.5, PM₁₀, temperature, wind speed, artificial light at night, and building density were significantly associated with increased odds of DS, while higher relative humidity, and higher greenness indicators (Normalized Difference Vegetation Index [NDVI], forest-shrub-grass coverage, and cropland coverage) were inversely associated. Among all exposures, building density showed the greatest contribution in the model ranking. Considering the joint impacts, unfavorable environmental profiles across all three domains were significantly associated with higher odds of DS, particularly among children with abnormal weight or higher metabolic risk. Importantly, population attributable fraction analysis indicates that improving environmental profiles could theoretically reduce 14.22-29.41% of DS cases, with geographical factors showing the largest theoretical contribution. These findings underscore the importance of incorporating environmental considerations into mental health strategies and support urban design and air quality improvements as tailored interventions for vulnerable populations to reduce the burden of DS.