OBJECTIVES: To determine the impact of Medical Marijuana Legalization on prescription opioid utilization.

METHODS: A 10% sample of a nationally representative database of commercially insured population was used to gather information on opioid use, chronic opioid use and high-risk opioid use for the years 2006-2014. Adults with pharmacy and medical benefits for the entire calendar year were included in the population for that year and the same individual could be included in the population for multiple years. Multilevel logistic regression analysis, controlling for patient level and state level factors, were used to determine the impact of Medical Marijuana Legalization on the three opioid use measures. Sub-group analysis among cancer-free adults, and cancer-free adults with at least one chronic non-cancer pain condition were conducted. Alternate start date for medical marijuana legalization, using a fixed effects regression model, and a falsification test were used to test the robustness of our results.

RESULTS: Medical Marijuana Legalization was found to be associated with a lower odds of any opioid use: OR=0.95 (0.94-0.96), chronic opioid use: OR=0.93 (0.91-0.95) and high-risk opioid use: OR=0.98 (0.96-0.99). The findings were similar in both the sub-group analysis and all the sensitivity analysis.

CONCLUSIONS: In states where marijuana is available through medical channels it may be substituting opioids for pain management. Policy makers could consider Medical Marijuana Legalization as a tool to curb chronic and high-risk opioid use. However, further research assessing risk versus benefits of medical marijuana legalization and head to head comparisons of marijuana versus opioids for pain management is required.