J-Shaped Association Between Sleep Timing and Suicidal Ideation: A Nationwide Cross-Sectional Study

Adolescent suicide has emerged as a global public health concern. Among various risk factors for suicide, sleep-particularly sleep timing-is valuable for its modifiability. However, the relationship between sleep timing and suicidality remains unclear. This study aimed to explore the association between sleep timing and suicidal ideation among Korean adolescents.

This cross-sectional study analyzed data from 759,350 adolescents who participated in the Korea Youth Risk Behavior Web-based Survey from 2007 to 2019. Self-reported weekday sleep timing (categorized by "go-to-bed" times from 8 PM to 3 AM) and suicidal ideation were analyzed. Hierarchical multivariable logistic regression was performed to evaluate the association between sleep timing and suicidal ideation, adjusting for potential confounders, including sleep duration, sleep quality, and depressive mood.

Of the 759,350 adolescents, 17.4% reported suicidal ideation. Using 11 PM as the reference, both the early sleep timing (8 PM: OR = 1.54, 95% CI = 1.29-1.84) and late sleep timing (3 AM: OR = 2.17, 95% CI = 2.09-2.26) were associated with higher odds of suicidal ideation, demonstrating a J-shaped relationship. This independent association remained after adjusting for sociodemographic factors, sleep duration, sleep quality, and depressive mood. The J-shaped pattern appeared consistently across sex and school level. Age-stratified analyses also showed a consistent J-shaped pattern across all ages, with the nadir shifting slightly later with age (from 10 PM in younger adolescents to midnight in older adolescents).

A J-shaped association between sleep timing and suicidal ideation was observed after controlling for sleep duration, sleep quality, and depressive mood. These findings indicate that sleep timing may serve as a candidate behavioral marker associated with suicidal ideation. Further longitudinal and intervention studies are warranted to confirm temporality and clarify underlying mechanisms.