Background: The coronavirus disease 2019 (COVID-19) pandemic has negatively impacted many aspects of life. Measures for preventing the spread of COVID-19 (e.g., school lockdowns, remote and hybrid classes, group and outdoor activity restrictions, and social distancing in the classroom and meal time) could have led to adolescents to experience anxiety and depressive symptoms. Such mental health impacts could increase the risk of suicidal ideation in this population. Moreover, according to a report by the Organization for Economic Co-operation and Development, although the total number of suicide deaths in South Korea decreased in 2021, the suicide rate of those aged 10–29 years increased. One factor affecting the result is adolescent mental health by COVID-19. This study examines the mental health status of South Korean adolescents amid the prolonged COVID-19 pandemic, and identifies and analyzes predictors of suicidal ideation, suicide planning, and suicide attempts. Methods: The study used data from 54,948 adolescents who participated in the 2020 Korea Youth Risk Behavior Web-based Survey. Based on their responses to suicide-related questions, the sample was divided into a healthy group, suicide-ideation group, suicide-planning group, and suicide-attempt group. The descriptive statistics of these groups were then analyzed. An analysis of covariance, post-hoc tests, and multiple logistic regression analysis were performed on the four groups. Results: Overall, 6.9% of the participants reported suicidal ideation, 2.2% reported planning suicide, and 1.9% reported attempting suicide in the previous 12 months. Conclusions: During the prolonged COVID-19 pandemic, there is a strong need for various individualized programs that identify and intervene to support adolescents at risk of suicide by accurately assessing their mental health risk factors, such as stress, sadness and despair, loneliness, and generalized anxiety disorder. Accordingly, it is necessary to develop and distribute a mental health and well-being curriculum, strengthen suicide prevention programs and support services, expand mental health diagnostic tests, and school-based mental health programs.

Background/Objectives: 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. Methods: 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. Results: 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). Conclusions: 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.