Bilateral associations between sleep duration and depressive symptoms among Chinese adolescents before and during the COVID-19 pandemic.

Depression is one of the most prevalent psychiatric disorders and the leading cause of disability among adolescents, with sleep duration as its vital influential factor. Adolescents might be mentally sensitive to the stress caused by the COVID-19 pandemic. Yet, the alteration of adolescents' sleep duration, depression, and their associations within the context of the COVID-19 pandemic have not been well documented. We conducted a longitudinal study, recruiting 2496 adolescents from 3 junior high schools to examine the alteration of their sleep duration and depressive symptoms before and during the pandemic, and to explore their potential association(s). Data were collected before (December 2019) and during the pandemic (July 2020). Paired samples t-test revealed a significant decrease in sleep duration and a significant increase in depressive symptoms during the COVID-19 pandemic. Higher grades, COVID-19 infection history, higher CES-DC score, and the COVID-19 pandemic itself might contribute to decreased sleep duration, while longer exercise duration during the pandemic might be a protective factor. According to the cross-lagged analysis, the existence of depressive symptoms before the pandemic was significantly associated with a shorter sleep duration during the pandemic (β = -0.106, p < 0.001). Previously shortened sleep duration was significantly associated with a greater likelihood of depressive symptoms during the pandemic (β = -0.082, p < 0.001). Our findings revealed that the COVID-19 pandemic has a negative influence on adolescents' mental health and sleep. Mental preparedness should be highlighted to mitigate the psychosocial influences of any possible public emergencies in the future. Sleep duration represents a viable home-based intervention for depressive symptoms.