The effect of youth marijuana use on high-risk drug use: Examining gateway and substitution hypothesis

Youth high-risk drug use causes harm to individuals and raises social concerns in the United States (US). To prevent youth high-risk drug use effectively, it is crucial to identify and address the significant risk factors. Some view the use of low-risk drugs (e.g., marijuana) as one such risk factor, though studies posit conflicting arguments about the effect of youth marijuana use. Some argue that youth marijuana use is a gateway to high-risk drug use; therefore, youth marijuana use boosts the likelihood of high-risk drug use. However, others postulate that there is a substitution effect of youth marijuana use, in which youth marijuana use replaces and, therefore, reduces their high-risk drug use. Our study aims to clarify these two conflicting arguments by examining the following hypotheses: (i) there is a significant discrepancy in youth high-risk drug use between marijuana-using youths and non-marijuana-using youths, and (ii) youths who consume marijuana are significantly more likely to use high-risk drugs after controlling for individual and environmental characteristics. To test our hypotheses, we analyzed nationally representative youth survey data collected between 2010 and 2019, determining the annual average comparison and performing comparative multiple regression analyses. The results from these analyses show that there is a significant gateway effect of youth marijuana use, with youth marijuana use significantly increasing high-risk drug use after controlling for individual and environmental risk factors. Considering the recent marijuana legalization trends in the US, this finding suggests that policymakers should pay close attention to the gateway effect of youth marijuana use.