Association between chronotype and psychological health in South Korean adolescents

Abstract Background. Chronotype influences general health. Among the early, intermediate, and late chronotypes, the latter is positively associated with psychological problems. However, longitudinal studies on the topic are relatively limited. We assessed the association between chronotype and the mental health of adolescents, focusing on depression and somatic symptoms by cross-sectional and longitudinal analyses. Methods. This longitudinal study relied on data from the KCYPS (Korean Children and Youth Panel Survey), which targeted middle school students. The sample consisted of 1,882 students who were assessed annually over a span of four years, from 2018 to 2021. The main exposure variable, chronotype, was determined by analyzing participants' sleep onset and wake times. The outcome variables, depression and somatic symptoms, were evaluated using the SCL-90 (Symptom Checklist-90) for depression and an emotional or behavioral problems questionnaire for children to assess somatic symptoms. Multilevel linear regression analysis was conducted both concurrently and prospectively, with gender stratification. Results. Late chronotype was found to be associated with depression and somatic symptoms within the same year (Depression β=0.062, p=<.001; Somatic symptoms β=0.056, p=.018), and it also proved predictive of somatic symptoms one year later (β=0.055, p=.019). In males, insufficient sleep exacerbated the adverse effects of late chronotype on depression one year later (β=0.100, p=.042), and late chronotype was a predictor of somatic symptoms one year later (β=0.072, p=.024). On the other hand, in females, late chronotype was only correlated with depression and somatic symptoms within the same year (Depression β=0.061, p=.025; Somatic symptoms β=0.075, p=.005). Conclusions. The late chronotype exhibited a negative impact on depression/somatic symptoms and proved to be predictive of somatic symptoms one year later. In females late chronotype was only concurrently related to mental health but in males it could predict mental health a year later, with moderation of insufficient sleep. These results provide insight into the relationship between chronotype and somatic symptoms and suggest that the negative impact of chronotype on the mental health of adolescents can be modulated.