Abstract
<title>Abstract</title> <p>Introduction Childhood depression is an important public health concern in China, where rapid socioeconomic changes may contribute to earlier onset. However, evidence specific to primary school students remains limited. This study examined temporal trends and associated factors of depressive symptoms among Chinese primary school students. Methods Five survey waves were conducted among primary school students in Taizhou, Zhejiang Province, China, between May 2021 and March 2023. Depressive symptoms were assessed using the Children’s Depression Inventory. The study included 36,116 person-wave observations using a repeated cross-sectional design with a nested longitudinal subsample of 9,212 students. Temporal trends were examined using Cochran-Armitage trend tests, and generalized linear mixed-effects models identified associated factors. Results The prevalence of depressive symptoms decreased significantly from 12.1% in May 2021 to 4.1% in March 2023 (P for trend < 0.001), with the steepest decline between the first two waves. In multivariable analyses, poor parent–child relationships showed the strongest association with depressive symptoms (OR = 6.00, 95% CI: 4.27–8.44), followed by study difficulties (OR = 3.71, 95% CI: 3.23–4.26). Excessive screen time, prolonged study time, and socioeconomic disadvantage were also significant risk factors, while regular physical activity was protective. The association between poor family economic status and depressive symptoms strengthened over time, indicating a time-varying effect of socioeconomic disadvantage. Conclusions Depressive symptoms among primary school students in Eastern China declined substantially from 2021 to 2023. Family relationships, academic difficulties, behavioral factors, and socioeconomic disadvantage remain key correlates, highlighting the need for multilevel interventions targeting family, school, and structural determinants.</p>