Abstract Body (Do not enter title and authors here): Background: Chronotype influences general health, with late chronotypes often linked to psychological problems. However, longitudinal studies on this topic are limited. This study assessed the association between chronotype and adolescent mental health, focusing on depression and somatic symptoms through cross-sectional and longitudinal analyses.
Methods: This longitudinal study used data from the Korean Children and Youth Panel Survey (KCYPS), targeting middle school students aged 13. Participants were assessed annually over four years (2018-2021). Chronotype was determined by analyzing sleep onset and wake times. Depression and somatic symptoms were evaluated using preexisting questionnaires like the SCL-90. Multilevel linear regression analyses were conducted both concurrently and prospectively, with gender stratification. Covariates included sleep quality, physical activity, smartphone usage, breakfast and friendship.
Results: The study included 1,882 students who completed all follow-ups. Students with a late chronotype, short sleep duration, and low sleep quality reported more mental health symptoms. Late chronotype was associated with higher levels of depression (β=0.062, p<.001) and somatic symptoms (β=0.056, p=.018) within the same year, and predicted somatic symptoms one year later (β=0.055, p=.019). For males, insufficient sleep worsened the effects of late chronotype on depression one year later (β=0.100, p=.042), and late chronotype predicted somatic symptoms one year later (β=0.072, p=.024). In females, late chronotype was associated with depression (β=0.061, p=.025) and somatic symptoms (β=0.075, p=.005) within the same year but did not predict future symptoms.
Conclusions: Late chronotype negatively impacted depression and somatic symptoms and predicted future somatic symptoms. In females, late chronotype was related only to current mental health issues, whereas in males, it predicted future mental health problems, especially when combined with insufficient sleep. These findings highlight the impact of chronotype on adolescent mental health and suggest that its negative effects can be moderated by factors like sleep duration.