Combined patterns of physical activity, screen-based sedentary behaviour, and sleep duration and their associations with depressive symptoms in Chinese adolescents

Background: Depression is a growing public health burden and is one of the leading causes of disability and illness in adolescents. Lifestyle factors are associated with depressive symptoms (DSs) in adolescents. This study aimed to estimate the prevalence of DSs and investigate the independent and combined associations between DSs and moderate-to-vigorous physical activity (MVPA), screen-based sedentary time (ST), and sleep duration (SLD) among Chinese adolescents aged 11–19 years. Methods: Repeated cross-sectional data were collected through questionnaires on health status and influencing factors for high school students in Ningbo, China, from a school-based study conducted from September to October in 2022 and in 2023. A multistage, stratified cluster sampling procedure was used to select target adolescents aged 11–19 years. DSs were assessed using the Centre for Epidemiological Studies Depression Scale. A multivariate analysis was used to assess the associations between independent lifestyle behaviours (MVPA, ST, and SLD) and the combined patterns of those lifestyle behaviours with DSs. Results: The prevalence of DSs amongst the adolescents was 16.3%. Low MVPA, excessive ST, and short SLD were independently associated with a greater likelihood of DSs (all p < 0.001). The unhealthiest combined pattern of low MVPA, excessive ST, and short SLD was associated with the highest odds of DSs (OR:4.2, 95% CI:3.3, 5.2, p < 0.001). In addition, the other combined patterns of MVPA, sleep duration, and ST were significantly associated with an increase in DSs compared with the healthy combined patterns of high MVPA, appropriate ST, and sufficient SLD. Conclusion: Our results indicate that MVPA, ST, and SLD were independently and in combination associated with an increase in DSs. Effective school-based health education programmes aimed at promoting healthy lifestyles are necessary to protect the mental health of Chinese adolescents. Future longitudinal studies are needed to confirm causality between the combined lifestyle patterns and DSs in Chinese adolescents.