Association Between Smartphone Screen Time and Mental Health Among Korean Adolescents: A National Representative Study

Objective Evidence linking smartphone use to adverse mental health outcomes is increasing, but the association between screen time and adolescent mental health remains unclear. Thus, this study aimed to examine these associations among adolescents in South Korea.Methods We analyzed data from students aged 12–18 years who participated in the Korean Youth Risk Behavior Web-based Survey from 2020 to 2024. Smartphone screen time was grouped as 4 hours per day, and mental health outcomes (loneliness, depressive mood, and perceived stress) were assessed using self-reported measures. Associations between smartphone screen time and mental health were examined using weighted logistic regression, yielding weighted odds ratios (wORs) and 95% confidence intervals (CIs). We further examined socio-demographic and behavioral subgroups that were particularly vulnerable.Results Among 231,292 participants (48.92% girls), daily smartphone use was 8.39% for 4 hours per day. Adolescents using smartphones for >4 hours per day had higher odds of loneliness (wOR, 1.43 95% CI, 1.36– 1.51), depressive mood (1.31 1.26–1.37), and perceived stress (1.11 1.07–1.16) than those using smartphones for <2 hours. Subgroup analyses showed that the associations were particularly pronounced among middle school students, girls, and those with higher socioeconomic status, higher academic performance, and longer sleep duration, especially for loneliness and depressive mood.Conclusion Our nationally representative findings suggest that excessive smartphone use is substantially associated with adverse mental health outcomes among Korean adolescents. These results highlight the importance of developing targeted interventions and public health strategies to promote healthy digital behaviors.