Nonmedical drug use and suicidal ideation among adolescents in the Republic of Korea: a population-based study.

Nonmedical drug use (NMU) among adolescents is an emerging public-health concern; however, population-based evidence on its association with suicidal ideation in the Republic of Korea remains limited. Using pooled data from the 2022-2024 Korea Youth Risk Behavior Survey (N = 158,829), we examined factors associated with lifetime NMU and its cross-sectional association with suicidal ideation during the previous 12 months using complex-samples logistic regression. A total of 2348 adolescents reported lifetime NMU (weighted prevalence, 1.6%; 95% CI  1.5-1.6%). Suicidal ideation was reported by 46.1% of adolescents with NMU and 12.8% of those without NMU. In fully adjusted models, NMU was associated with high perceived stress, higher GAD-7 total score, depressive symptoms, sexual intercourse experience, and alcohol blackout in the previous 30 days. After sequential adjustment for psychological distress and co-occurring health-risk behaviors, NMU remained associated with suicidal ideation (adjusted odds ratio = 2.55, 95% CI  2.27-2.87; P < 0.001). In the fully adjusted model, the adjusted predicted probability of suicidal ideation was 23.2% (95% CI  21.7%-24.7%) among adolescents with NMU and 13.1% (95% CI  12.9%-13.3%) among those without NMU, corresponding to an absolute difference of 10.1% points (95% CI  8.6-11.7). These findings indicate that lifetime NMU is associated with psychological distress, co-occurring health-risk behaviors, and suicidal ideation at the population level. Given the cross-sectional design and differing reference periods of the measures, the results should be interpreted as associations rather than evidence of temporal or causal relationships.