The enactment of medical marijuana laws in the United States was not found to be associated with a reduction in the use of nonmedical prescription opioids or in prescription opioid use disorder (OUD), according to study results published in JAMA Network Open.

Investigators sought to determine whether state-level legalization was associated with changes in illicit use of prescription opioids or prescription opioid-related OUD, as well as whether such changes varied by age or race/ethnicity.

In this cross-sectional study, the de-identified data from the population-based National Survey on Drug Use and Health, which took place between 2004 and 2014 and included 627,000 individuals aged ≥12 years (51.51% women; 9.88% aged 12-17 years, 13.30% aged 18-25 years, 14.30% aged 26-34 years, 25.02% aged 35-49 years, and 37.50% aged ≥50 years; 66.97% white, 11.83% black, 14.47% Hispanic, and 6.73% other) were examined.

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The study’s primary exposure was enactment of medical marijuana laws at the state level, and the study’s outcomes were the rates of nonmedical use of prescription opioids and prescription OUD in nonmedical users, both over the previous year.

Participant response rates were 82% to 91% and 71% to 77% for the screening and interview processes, respectively. Following medical marijuana legalization, nonmedical prescription opioid use increased slightly overall, with prevalence rates rising from 4.32% before legalization to 4.86% afterward (adjusted odds ratio [aOR], 1.13; 95% CI, 1.06-1.20), and there was a small nonsignificant decrease in the prevalence of prescription OUD, from 15.41% to 14.76% (aOR, 0.95; 95% CI, 0.81-1.11). Similar results were seen across all ages and races/ethnicities.

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Study strengths include high-quality data, good representation of multiple age groups, and an adjustment for potential confounders. Study limitations include the use of self-reported outcome measures, an inability to explore the most recent survey years, the exclusion of certain populations, and the lack of control for the effects of recreational marijuana legalization.

“Our results suggest that if [medical marijuana laws] do have any effect on opioid-related outcomes, it likely does not occur through reducing individual-level [nonmedical use of prescription opioids],” noted the authors. They recommended that future research examine mechanisms through which legalization may help mitigate opioid-related harm.

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Segura LE, Mauro CM, Levy NS, et al. Association of US medical marijuana laws with nonmedical prescription opioid use and prescription opioid use disorder. JAMA Netw Open. 2019;2(7):1-11. doi:10.1001/jamanetworkopen.2019.7216