National trends in alcohol and substance use among adolescents from 2005 to 2021: a Korean serial cross-sectional study of one million adolescents

BACKGROUND: Although previous studies have provided data on early pandemic periods of alcohol and substance use in adolescents, more adequate studies are needed to predict the trends of alcohol and substance use during recent periods, including the mid-pandemic period. This study investigated the changes in alcohol and substance use, except tobacco use, throughout the pre-, early-, and mid-pandemic periods in adolescents using a nationwide serial cross-sectional survey from South Korea. METHODS: Data on 1,109,776 Korean adolescents aged 13–18 years from 2005 to 2021 were obtained in a survey operated by the Korea Disease Control and Prevention Agency. We evaluated adolescents’ alcohol and substance consumption prevalence and compared the slope of alcohol and substance prevalence before and during the COVID-19 pandemic to see the trend changes. We define the pre-COVID-19 period as consisting of four groups of consecutive years (2005–2008, 2009–2012, 2013–2015, and 2016–2019). The COVID-19 pandemic period is composed of 2020 (early-pandemic era) and 2021 (mid-pandemic era). RESULTS: More than a million adolescents successfully met the inclusion criteria. The weighted prevalence of current alcohol use was 26.8% [95% confidence interval (CI) 26.4–27.1] from 2005 to 2008 and 10.5% (95% CI 10.1–11.0) in 2020 and 2021. The weighted prevalence of substance use was 1.1% (95% CI 1.1–1.2) from 2005 to 2008 and 0.7% (95% CI 0.6–0.7) between 2020 and 2021. From 2005 to 2021, the overall trend of use of both alcohol and drugs was found to decrease, but the decline has slowed since COVID-19 epidemic (current alcohol use: β(diff) 0.167; 95% CI 0.150–0.184; substance use: β(diff) 0.152; 95% CI 0.110–0.194). The changes in the slope of current alcohol and substance use showed a consistent slowdown with regard to sex, grade, residence area, and smoking status from 2005 to 2021. CONCLUSION: The overall prevalence of alcohol consumption and substance use among over one million Korean adolescents from the early and mid-stage (2020–2021) of the COVID-19 pandemic showed a slower decline than expected given the increase during the prepandemic period (2005–2019). SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s12519-023-00715-9.