The legalization of medical marijuana appears to be linked with a slight decrease in the use of nonprescribed pharmaceutical opioids, according to a recent study published in the International Journal of Mental Health and Addiction. The study, conducted by researchers from Rutgers and Columbia universities and the University of Arizona’s School of Government and Public Policy, suggests that this could be due to a “substitution effect,” where individuals partially replace opioids with cannabis.
The decrease in opioid use, while modest—ranging from approximately 0.6 percent to 1.5 percent for regular to frequent opioid use—was primarily observed in individuals diagnosed with cannabis use disorder. The researchers emphasized that these findings underscore the importance of recognizing the potential trade-offs associated with cannabis legalization as a strategy to mitigate opioid-related harm.
The study analyzed national survey data from 2004 to 2014, focusing on nonmedical prescription opioid (NMPO) use, which refers to the use of prescription opioids without a prescription or in a manner other than prescribed. Interestingly, the study also found that medical cannabis legalization (MCL) was associated with a 2.1 percent increase in the occasional use of nonmedical prescription opioids, defined as usage between once and 12 times per year.
A deeper analysis of the findings revealed that individuals with cannabis use disorder (CUD) were primarily driving this trend. Among this group, frequent opioid use (defined as weekly to daily usage) decreased by 4.9 percent following the implementation of medical marijuana laws, while occasional use increased by 5.6 percent. Hillary Samples, the lead author of the study and a professor of health systems and policy at the Rutgers School of Public Health, noted that while the main results suggest people may be substituting opioids with cannabis, the decrease in opioid use is modest and confined to high-risk marijuana users. She stated that this might be worth considering from a harm-reduction perspective, but it is far from being the only solution to the opioid problem.
Samples suggested that legal access to medical cannabis might offer some benefits in the context of opioid-related harm, but emphasized that there are more effective interventions to address the ongoing overdose crisis, such as increasing access to treatment for opioid addiction. The study concluded that while the implementation of MCL has some potential to reduce the risk of opioid-related morbidity and mortality in high-risk groups with cannabis addiction, these findings should be interpreted within the broader context of literature on the association of MCL with cannabis outcomes and on the association of individual-level cannabis use with adverse opioid-related outcomes. Despite the modest impact on the ongoing opioid overdose epidemic, these findings contribute to a growing body of research suggesting that legal access to cannabis can reduce various forms of opioid use.
For instance, a federally funded study in August found that marijuana was significantly associated with reduced opioid cravings for people using them without a prescription. Another study found that legal access to CBD products led to significant reductions in opioid prescriptions, with state-level drops of between 6.6 percent and 8.1 percent fewer prescriptions. Furthermore, a report from this summer linked medical marijuana use to lower pain levels and reduced dependence on opioids and other prescription medications. The American Medical Association (AMA) also released research showing that about one in three chronic pain patients report using cannabis as a treatment option, and most of that group has used cannabis as a substitute for other pain medications, including opioids. In conclusion, while the impact of medical marijuana legalization on opioid use is modest and primarily observed in high-risk groups, the findings add to the growing body of evidence suggesting that cannabis could potentially serve as a safer substitute for opioids. However, the researchers stress the need for further research to better understand the implications and trade-offs of cannabis legalization.