Abstract
<title>Abstract</title> <p>Introduction: Adolescent substance use (smoking, marijuana, and amphetamine) is associated with adverse physical, mental, behavioral, and social outcomes and remains a global public health concern, including in Thailand. Parental monitoring, a fundamental component of the parent-child relationship, plays a crucial role in reducing adolescent substance use. We investigated the effect of parental monitoring on adolescents’ substance use and explored the potential moderating role of adolescents' anxiety. Methods This cross-sectional study used data from the 2021 Thailand Global School-Based Student Health Survey (GSHS), which included 5661 school-going adolescents aged 13–17 years in grades 7–12. To assess the association between parental monitoring and substance use, both univariate and multivariable logistic regressions were performed, adjusting for potential confounders and complex sampling. Effect measure modification by anxiety was examined by adding an interaction term on a multiplicative scale. Results Overall, 82.7% of adolescents reported that their parents were aware of their free-time activities. The prevalence of current smoking, current marijuana use, and lifetime amphetamine/methamphetamine use was 11.4%, 4.9%, and 3.7%, respectively. Parental monitoring significantly lowered the odds of current smoking (AOR: 0.67, 95% CI 0.49, 0.93) and current marijuana use (AOR: 0.60, 95% CI 0.39, 0.90), but not amphetamine use (AOR: 0.79, 95% CI 0.51, 1.24). We found no significant evidence of effect measure modification by anxiety on a multiplicative scale. Conclusions The findings highlight the protective role of parental monitoring against adolescent substance use and call for further research examining a broader range of parental factors to guide effective public health interventions.</p>