Medical Marijuana Laws Do Not Boost Recreational Use Among Teens

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Study findings report that contrary to popular beliefs, legalizing medical cannabis has not increased recreational marijuana use among teenagers in the United States.

Since the enactment of the first medical marijuana law in 1996, the public has debated whether recreational marijuana use would increase among teenagers.

“The topic is important to study because regular use of marijuana in teens is associated with many long-term problems, including reduced neurodevelopment, IQ, educational and occupational achievements,” Deborah S. Hasin, PhD, from the departments of epidemiology and psychiatry, Columbia University College of Physicians and Surgeons, Mailman School of Public Health, told Healio Psychiatry.

“Empirical evidence can inform this debate,” Hasin and colleagues wrote in their article published in Addiction. “Given how rapidly U.S. state marijuana laws are changing, a comprehensive review of the empirical literature is needed to provide a foundation for further research in this high-priority area.”

The researchers performed a systematic review and meta-analysis of studies to determine how legalizing medical marijuana in the U.S. affects marijuana use among teens. They screened almost 3,000 clinical papers, and meta-analyzed 11 studies, developed from four large, ongoing national surveys. Specifically, the 11 studies the investigators reviewed compared pre-post changes in states with medical marijuana laws to changes in states without legal medical marijuana use over comparable time-periods to estimate the effects of the laws on any past-month marijuana use prevalence.

The results showed no significant increases or decreases in adolescent recreational use following the legalization of medical marijuana. Meta-analysis revealed that none of the studies demonstrated significant changes in marijuana use prevalence among teens pre-post enactment of medical marijuana laws compared with simultaneous changes in states without medical marijuana laws (standardized mean difference = –0.003).

“While medical marijuana laws did not increase the risk for marijuana use in teens so far, that does not diminish the potential seriousness of regular or heavy early use, which requires clinical attention in states with and without medical marijuana laws,” Hasin told Healio Psychiatry.

Of 11 studies included in the meta-analysis, all studies that compared states with and without legalized medical marijuana found that states with medical marijuana laws had higher rates of past-month marijuana use before the passage of such laws. Although the impact of legalizing medical cannabis on additional marijuana outcomes and subgroups produced nonsignificant results, limited heterogeneity warrants further study, according to the authors.

“For now, there appears to be no basis for the argument that legalizing medical marijuana has increased teens’ use of the drug. However, we may find that the situation changes as commercialized markets for medical marijuana develop and expand, and as states legalize recreational marijuana use,” Hasin said in a press release. “This warrants additional consideration, especially with the decreasing national trend of risk perception among adolescents and as the current perception gives rise to more medical marijuana stores and commercial opportunities.”

On the other hand, other evidence indicated that more adults may use marijuana recreationally after the passage of medical marijuana laws, according to Hasin.

“The $8 billion cannabis industry anticipates tripling by 2025,” she said in the release. “Obtaining a solid evidence base about harmful, as well as beneficial, effects of medical and recreational marijuana laws on adults is crucial given the intense economic pressures to expand cannabis markets.”