Opioid prescriptions dropped in states where medical marijuana is legal—suggesting some U.S. residents might use marijuana to treat their pain as an alternative to opioids, according to two separate studies published Monday in JAMA Internal Medicine.
Association between medical marijuana laws and opioid use
For the first study, researchers from the University of Georgia examined the association between medical marijuana legalization in states and opioid prescriptions filled under Medicare Part D. To do so, they analyzed Medicare Part D data from 2010 to 2015 in all U.S. states and Washington D.C., including the 29 states and Washington D.C. that have laws legalizing medical marijuana use.
The researchers found states that implemented medical marijuana laws saw opioid prescribing decline by 8.5%, compared with those without such laws. Specifically, they found the number of filled opioid prescriptions dropped by 2.21 million daily doses annually when states implemented medical marijuana laws. The researchers also examined whether the association varied by type of medical marijuana law, focusing on those that allow for active medical marijuana dispensaries and those that allow individuals to cultivate the drug at home. They found the number of filled opioid prescriptions dropped by:
- 3.74 million daily doses annually when states implemented laws allowing dispensaries; and
- 1.79 million daily doses annually when states implemented laws allowing home cultivation.
The researchers also found morphine use and hydrocodone decreased by 20.7% and 17.4%, respectively, in states that allow medical marijuana dispensaries.
The researchers wrote, "Combined with previously published studies suggesting cannabis laws are associated with lower opioid mortality, these findings further strengthen arguments in favor of considering medical applications of cannabis as one tool in the policy arsenal that can be used to diminish the harm of prescription opioids."
They concluded, "[A] growing consensus suggests that cannabis can be used to effectively manage pain in some patients. If initial licit prescriptions for opioids can be reduced, then there is a plausible theoretical pathway to anticipate that opioid misuse and abuse could also fall."
Association between medical marijuana laws and Medicaid prescription rates for opioids
For the second study, researchers from University of Kentucky and Emory University examined the association between states implementing medical marijuana laws and adult-use marijuana laws and opioid prescription rates and spending among Medicaid beneficiaries. To do so, the researchers analyzed CMS data from 2011 to 2016.
The researcher found that medical marijuana laws were associated with a 5.88% reduction in Medicaid opioid prescribing rates, while states with adult-use marijuana laws were associated with a 6.38% reduction in Medicaid opioid prescribing rates.
According to the study, states that implemented medical marijuana laws saw 39.41 fewer opioid prescriptions per 1,000 Medicaid beneficiaries annually. When states with existing medical marijuana laws implemented adult use laws, opioid prescriptions fell by a further 6.38%.
In comparison, the average annual Medicaid-covered opioid prescribing rate in states without such laws was 670.16 per 1,000 Medicaid beneficiaries, according to the study.
The researchers also found that medical and adult-use marijuana laws were "associated with a lower rate of Medicaid-covered prescriptions for non-opioid pain medications of 8.36% and 8.69%, respectively."
The researchers concluded, "Marijuana is one of the potential alternative drugs that can provide relief from pain at a relatively lower risk of addiction and virtually no risk of overdose." They wrote, "Medical and adult-use marijuana laws have the potential to lower opioid prescribing for Medicaid enrollees, a high-risk population for chronic pain, opioid use disorder, and opioid overdose, and marijuana liberalization may serve as a component of a comprehensive package to tackle the opioid epidemic."
Hefei Wen, an assistant professor at the University of Kentucky involved in the second study, said, "Our study provides some of the first empirical evidence that the implementation of medical and adult-use marijuana laws between 2011 and 2016 was associated with lower opioid prescribing rates and spending among Medicaid enrollees, a high-risk population for chronic pain, opioid use disorder, and opioid overdose."
However, W. David Bradford, the Busbee Chair in Public Policy in the Department of Public Administration and Policy at the University of Georgia who was involved in the first study, urged caution in interpreting the study findings. "We do know that cannabis is much less risky than opiates, as far as likelihood of dependency," but "it is not without risks." He continued, "Like any drug in our FDA-approved pharmacopeia, it can be misused. ... So I hope nobody reading our study will say 'Oh, great, the answer to the opiate problem is just put cannabis in everybody's medicine chest and we are good to go.' We are certainly not saying that."
Mark Olfson, a professor of psychiatry and epidemiology at Columbia University who authored a study on the marijuana use and the risk of opioid use disorders in the United States, said "[T]here may be a role—and there likely is a role—for medical marijuana in reducing the use of prescribed opioids for the management of pain." But he cautioned that it does not eliminate the potential for opioid misuse. Olfson and his colleagues in their study found marijuana users are six times more likely than non-marijuana uses to misuse opioids.
Kevin Hill, an addiction psychiatrist at Beth Israel Deaconess Medical Center and an assistant professor of psychiatry at Harvard Medical School, and Andrew Saxon, a psychiatry professor at the University of Washington, in invited commentary published in JAMA Internal Medicine wrote, "For many reasons, ranging from significant barriers to research on cannabis and cannabinoids to impatience, cannabis policy has raced ahead of cannabis science in the United States." They continued, "This situation has to change to get definitive answers on the possible role for cannabis in the opioid crisis, as well as the other potential harms and benefits of legalizing cannabis" (Angell, Forbes, 4/2; Harris, "Shots," NPR, 4/2; Fox, NBC News, 4/2; George, MedPage Today, 4/2; Bradford et al., JAMA Internal Medicine, 4/2; Wen, JAMA Internal Medicine, 4/2).
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