Editor’s Note: This article originally appeared on the IASP Pain Research Forum, and has been lightly adapted for RELIEF.
The United States is in the midst of an opioid epidemic. The most recent statistics released by the US Centers for Disease Control and Prevention (CDC) show that, on average, 115 Americans die each day from overdoses of opioid drugs such as oxycodone and fentanyl, with 40 percent of those deaths involving a prescribed drug. Canada is suffering a similar epidemic, with a record number of unintentional opioid-related deaths in the first nine months of 2017.
Could the availability of legalized marijuana help ameliorate this epidemic? Two new studies, looking at two distinct populations of patients, suggest it could. The findings from both studies suggest that states that allow legal access to marijuana show a decrease in opioid prescribing in comparison to states that don’t.
While these studies cannot address a possible causal relation between legalization and effects on opioid prescribing, nor do they speak to whether medical marijuana effectively relieves pain, the findings do nonetheless offer the possibility that medical cannabis may be one tool to mitigate the current opioid crisis.
“We are facing a devastating epidemic of opioid-related deaths in both the United States and Canada. The sheer number of deaths is shocking,” says Mark Ware, McGill University, Montreal, Canada. “Given the size and scope of the problem, we have a moral responsibility to look at new ways we might reduce current opioid prescribing,” according to Ware, who is the executive director of the nonprofit Canadian Consortium for the Investigation of Cannabinoids.
The two studies appeared April 2, 2018 in the journal JAMA Internal Medicine, along with an invited commentary by Kevin Hill, Harvard Medical School and Beth Israel Deaconess Medical Center, Boston, US, and Andrew Saxon, University of Washington, Seattle, US.
Fewer opioid prescriptions
The first study, led by W. David Bradford, University of Georgia, Athens, US, examined the effects of implementation of state-approved medical cannabis laws (MCLs) on opioid prescribing. The study used Medicare Part D data from 2010 to 2015. Medicare Part D is a US federal government program that offers prescription drug benefits to Americans over the age of 65, as well as to individuals with disabilities.
“Some of our previous research looked at how state adoption of medical cannabis laws affects utilization of prescription drugs,” said Bradford. “We saw a big response in the pain medication category, but we didn’t know whether those results were related to less risky pain medications like non-steroidal anti-inflammatory drugs or the riskier opioids,” he said. “With this study, we wanted to nail down two things: Is it opioids specifically that show a drop when MCLs are in place? And does it matter what type of law the state has passed to see that kind of drop?”
First author Ashley Bradford and colleagues discovered that states that had enacted any kind of MCL showed a reduction of more than two million daily doses per year of all opioid filled prescriptions, compared with states without an active MCL. Though this result was not statistically significant, it was still a reduction of more than 8 percent.
When looking at MCLs by type, they saw that states offering access through medical cannabis dispensaries showed an even greater decrease, with the researchers noting a statistically significant 3.7 million daily dose decline per year, compared with having no MCL, representing a more than 14 percent reduction.
Access to cannabis via home cultivation laws, on the other hand, resulted in only 1.8 million fewer annual daily doses, or a statistically significant reduction of almost 7 percent.
When looking at the type of opioid prescribed, the authors saw statistically significant reductions in hydrocodone prescriptions. These dropped by more than 17 percent, or 2.3 million daily doses, when filled with dispensary-based MCLs, and dropped by more than 9 percent, or approximately 1.3 million daily doses, when filled with MCLs based on home cultivation only. Similarly, morphine prescriptions dropped by nearly 21 percent, or 360,000 daily doses, when filled with dispensary-based MCLs. When considered with the overall daily dose decline the researchers saw, these results suggest that ease of access to medical marijuana through regulated dispensaries may be an important policy consideration.
Consistent results from a second study
In the second study, Hefei Wen, University of Kentucky College of Public Health, Lexington, US, saw similar results using a separate data set. This study looked at the effect of MCLs, as well as recreational cannabis laws, using Medicaid opioid prescription data from 2011-2016. Medicaid provides health insurance, including prescription drug benefits, to low-income individuals and families in the US.
She and her colleague, Jason Hockenberry, Emory University, Atlanta, US, also reported a significant drop in opioid prescription rates in states that decriminalized marijuana use. This included a 6 percent decrease for all opioids in states with medical marijuana laws, equating to about 39 fewer opioid prescriptions per 1,000 Medicaid enrolees per year, along with an additional 6 percent decrease when states implemented laws allowing recreational use.
When looking at opioid type, the authors saw reductions mainly in Schedule II opioids (considered to have more potential for abuse) in states with recreational use laws, and decreases mainly in schedule III-V opioids in states with medical marijuana laws. Also, the authors did note variations in outcome when analyzing results by state.
“It was very interesting to see these reductions both in Medicare and Medicaid populations,” said Wen. “Yet it is important to be cautious. These are strong associations, but we cannot say for sure whether these marijuana laws actually caused the reduction in opioid prescriptions. We don’t know if individual patients did not use opioids because they had access to marijuana, or if that access to marijuana changed the way physicians prescribed the opioid drugs. There may be other factors that we don’t understand yet.”
For instance, as noted in the accompanying commentary from Hill and Saxon, both data sets came from government-subsidized programs, so the results may not generalize to other demographic groups. Also, the studies did not take into account factors such as race, level of education, disability, or prevalence of disease, which could have affected the results.
But despite those limitations, W. David Bradford says that both studies should make doctors, public health officials, and policy makers think twice before dismissing marijuana out of hand as a legal pain relief treatment—one that could help curb the current opioid epidemic.
“When you see the papers side by side, they really make the results stronger. And [Wen and Hockenberry] took it a step beyond by looking at recreational use as well,” he says. “What these studies suggest is when cannabis is available as a treatment option, the number of opioid prescriptions goes down. For all the concern and skepticism about cannabis, we know it’s a less risky option than opioids. You are less likely to become addicted or die from using it. Given the crisis with regard to opioid misuse and abuse, any tool that might help us get that under control should be looked at. It behooves us, as a country, to consider that cannabis may be one tool—perhaps just one tool out of many, but a tool—that could help us bend the curve away from opioid misuse.”
Marijuana for pain: more research needed
Ware says that the results from the two new studies did not surprise him—and should inspire people to “react quickly.”
“The mortality associated with [the opioid crisis] is unthinkable,” he says. “If marijuana is a viable alternative to opioids, and if we can get to the point where we can teach physicians how to use this drug most effectively and put it into practice, we have the potential to make a difference and save lives.”
But when and how should medical marijuana be used as a potential pain treatment? While a comprehensive review published by the US National Academies of Sciences, Engineering, and Medicine suggests that marijuana may offer potential for the treatment of chronic pain conditions, the answers to those questions remain unclear.
“We really don’t know the effectiveness of marijuana as a pain treatment for many different conditions,” says Wen. “We also don’t know the best way to administer marijuana.”
Margaret Haney, Columbia University Medical Center, New York City, US, has been studying the effects of marijuana for decades. She hopes the new studies will inspire further research on whether marijuana could be a viable pain treatment.
“Pain is very diverse. Cannabis may potentially be an effective treatment for certain types of pain under certain conditions. But it may not be for others,” she said. “We still don’t really know what types of cannabinoids [the active ingredients in cannabis] are best to treat different types of pain.”
“These studies show an extremely interesting association that needs to be followed up with carefully controlled [human] trials,” she continued. “Just because there are fewer opioid prescriptions being filled in states with MCLs doesn’t mean that these patients’ pain is being effectively treated. There’s still a lot more work and research that needs to be done before we should be talking about any kind of policy changes.”
Kayt Sukel is a freelance writer based outside Houston, Texas.