Comparing the Effects of Adequate and Insufficient Sleep on the Mental Health, Behavioral Outcomes, and Daily Lives of South Korean Adolescents

<b>Background/Objectives:</b> Adequate sleep is critical for adolescents' physical and mental health. However, academic demands and lifestyle habits lead to insufficient sleep among many adolescents. This study examined the relationship between sleep patterns and general characteristics, health behaviors, and mental health among South Korean adolescents. <b>Methods:</b> Data were obtained from the Korea Youth Risk Behavior Survey conducted by the Korea Disease Control and Prevention Agency, involving 21,283 students aged between 13 and 18 years. Self-reported sleep duration was categorized as adequate (8-10 h) or insufficient (less than 8 h on both weekdays and weekends), and 20 independent variables across demographic, socioeconomic, lifestyle, health-related behavioral, and psychological factors were analyzed. Multiple logistic regression analyses were conducted to evaluate the effects of insufficient sleep. <b>Results:</b> Insufficient sleep was more prevalent among female students (odds ratio [OR]: 2.064) and older students (OR: 16.588 for Grade 12 vs. Grade 7) and was associated with higher stress levels (OR: 4.338 for almost always vs. never), suicidal ideation (OR: 1.826), and unhealthy behaviors such as alcohol consumption (OR: 2.009), smoking (OR: 1.998), and smartphone overdependence (OR: 2.313 for severe vs. normal). In contrast, adolescents with adequate sleep reported greater happiness (OR: 4.167 for very much vs. not at all) and better academic performance (OR: 1.377 for very high vs. very low). <b>Conclusions:</b> The findings show that insufficient sleep significantly affects adolescent well-being, highlighting the need for tailored interventions and increased societal awareness. Future research should explore the mechanisms underlying gender differences and weekday-weekend sleep disparities to enhance sleep quality in this population.