Supplemental Material for: Association between intentional non-medical substance use and allergic diseases among Korean adolescents: a nationwide representative study

Thus, this study aimed to investigate the association between intentional non-medical substance use and the risk of three major allergic diseases (asthma, allergic rhinitis [AR], and atopic dermatitis [AD]) among Korean adolescents.</p><p dir="ltr"><b>Methods:</b>We analyzed data from the Korea Youth Risk Behavior Survey, a nationally representative, school-based survey, including 740,141 adolescents aged≥ 14 yearsfrom 2008–2014 and 2016–2019.

Intentional non-medical substance use was assessed via self-reported lifetime history and further categorized by recency and specific substance types, including butane gas, glues, stimulants, methamphetamine, excessive cough suppressants, or sedatives. Physician-diagnosed asthma, AR, and AD were evaluated as primary outcomes. Survey-weighted multivariable logistic regression analysis was performed to estimate adjusted odds ratios (aORs) with 95% confidence intervals (CIs), and comprehensive subgroup and stratified analyses were conducted to evaluate substance-specific effects across sociodemographic groups.</p><p dir="ltr"><b>Results:</b>Among 740,141 adolescents (males, 51.39%), lifetime non-medical substance use was significantly associated with increased odds of asthma (aOR, 1.73 [95% CI, 1.60–1.87]), while the association with AR was modest (1.07 [1.00–1.13]) and no significant association was observed for AD (1.05 [0.98–1.12]).