Treatment admissions for opioids, cocaine, and methamphetamines among adolescents and emerging adults after legalization of recreational marijuana

Abstract

Background: A public health concern stemming from recreational marijuana legalization (RML) is the idea that marijuana may act as a "gateway" drug among youth and young adults, where growing marijuana use will lead to increasing substance use disorder (SUD) for "harder" illicit drugs. This study investigates whether SUD treatment admissions for cocaine, opioids, and methamphetamines increased following RML enactment in Colorado and Washington for adolescents and emerging adults.

Methods: We entered annual 2008-2017 treatment admissions data from the SAMHSA Treatment Episode Dataset - Admissions (TEDS-A) into difference-in-differences models to investigate whether the difference in treatment admissions for cocaine, opioids, and methamphetamines among adolescents (12-17), early emerging adults (18-20), and late emerging adults (21-24) before versus after RML enactment differed between Colorado and Washington and states without RML.

Results: There was no significant difference (p < 0.05) between Colorado and Washington and other states in the pre- versus postlegalization trajectories of SUD treatment admissions for cocaine, opioids, or methamphetamines for adolescents (β = -0.152, 95% CI = -0.500, 0.196; β = -0.374, 95% CI = -1.188, 0.439; β = 0.787, 95% CI = -0.511, 2.084, respectively), early emerging adults (β = -0.153, 95% CI = -0.762, 0.455; β = 0.960, 95% CI = -4.771, 6.692; β = 0.406, 95% CI = -2.232, 3.044, respectively) or late emerging adults (β = -0.347, 95% CI = -1.506, 0.812; β = -4.417, 95% CI = -16.264, 7.431; β = 1.804, 95% CI = -2.315, 5.923, respectively).

Conclusion: RML in Washington and Colorado was not associated with an increase in adolescent or emerging adult SUD treatment admissions for opioids, cocaine, or methamphetamines. Future studies should extend this research to other states, other substances, for older adults, and over longer time periods; and consider how the effects of drug policies may differ across different jurisdictions.

Keywords: Cannabis; Gateway drug; Legalization; Marijuana; Substance use disorder; Treatment.