Medical marijuana laws and adolescent use of marijuana and other substances: Alcohol, cigarettes, prescription drugs, and other illicit drugs.

Drug Alcohol Depend. 2017 Dec 7;183:62-68. doi: 10.1016/j.drugalcdep.2017.10.021.

[Epub ahead of print]

Cerdá M¹, Sarvet AL², Wall M³, Feng T⁴, Keyes KM⁵, Galea S⁶, Hasin DS⁷.

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Highlights

•Substance use decreased among 8th graders after medical marijuana use was legalized.
•Substance use did not change among 10th graders following legalization.
•Prescription drug and cigarette use increased among 12th graders after legalization.

Abstract

BACKGROUND:

Historical shifts have taken place in the last twenty years in marijuana policy. The impact of medical marijuana laws (MML) on use of substances other than marijuana is not well understood. We examined the relationship between state MML and use of marijuana, cigarettes, illicit drugs, nonmedical use of prescription opioids, amphetamines, and tranquilizers, as well as binge drinking.

METHODS:

Pre-post MML difference-in-difference analyses were performed on a nationally representative sample of adolescents in 48 contiguous U.S. states. Participants were 1,179,372U.S. 8th, 10th, and 12th graders in the national Monitoring the Future annual surveys conducted in 1991-2015. Measurements were any self-reported past-30-day use of marijuana, cigarettes, non-medical use of opioids, amphetamines and tranquilizers, other illicit substances, and any past-two-week binge drinking (5+ drinks per occasion).

RESULTS:

Among 8th graders, the prevalence of marijuana, binge drinking, cigarette use, non-medical use of opioids, amphetamines and tranquilizers, and any non-marijuana illicit drug use decreased after MML enactment (0.2-2.4% decrease; p-values:<0.0001-0.0293). Among 10th graders, the prevalence of substance use did not change after MML enactment (p-values: 0.177-0.938). Among 12th graders, non-medical prescription opioid and cigarette use increased after MML enactment (0.9-2.7% increase; p-values: <0.0001-0.0026).

CONCLUSIONS:

MML enactment is associated with decreases in marijuana and other drugs in early adolescence in those states. Mechanisms that explain the increase in non-medical prescription opioid and cigarette use among 12th graders following MML enactment deserve further study.