The belief that expanding cannabis access plays a role in mitigating opioid use and abuse came under fire this week after a newly published paper in the journal PLoS ONE failed to replicate observational findings initially documenting this trend.
Both studies employed similar methodology. Investigators evaluated whether the passage of medical cannabis legislation was associated with later changes in opioid-related mortality. The first study, published in the “Journal of the American Medical Association” in 2014, reported that opioid overdose deaths fell significantly in the years following marijuana liberalization. By contrast, the most recent paper reports that this effect reversed over time. Authors also failed to identify a similar decline in opioid-related mortality in states that have more recently enacted medical marijuana-related laws.
Why the disparate results? One factor likely has to do with the differing inclusion criteria utilized in the two studies. While the 2014 paper assessed trends exclusively in states with operational medical marijuana access programs, investigators writing in PLoS ONE did not. Rather, they categorized numerous states with non-traditional medical marijuana laws — such as those jurisdictions that simply exempt specific patients who obtain black market CBD products from criminal prosecution — as “medical cannabis states.”
In other cases, states that have codified medical marijuana legislation, but have yet to establish regulated cannabis production or sales, were also included. Predictably, these states with only limited, or in some cases, no medical cannabis access whatsoever, failed to experience any statistically significant trends.
But before jumping to any conclusions based upon the findings of any single paper, it is important to acknowledge that dozens of additional peer-reviewed studies exist on this topic. Most, but not all, of this literature supports the cannabis substitution theory.
What’s even more important, is that longitudinal studies evaluating opioid use patterns in specific patient populations provide clear and consistent evidence of this phenomenon. In contrast to observational, population-based studies (such as those summarized above), which only seek to identify whether an association exists between the passage of medical cannabis laws and opioid use trends in the general population — this data explicitly assesses individual patients’ relationship with opioids following their registration in state-sponsored access programs.
In virtually all cases, these studies conclude that patients diagnosed with chronic pain and other debilitating conditions typically reduce, or in some cases, eliminate their use of opioids following their enrollment in state-sanctioned programs.
For example, researchers writing in the May 2019 edition of the journal Annals of Pharmacotherapy evaluated the use of opioids in 77 intractable pain patients newly enrolled in the Minnesota Medical Cannabis Program. Researchers reported “a statistically significant decrease in MME (milligram morphine equivalents) from baseline to both three and six months.”
A 2018 study assessing prescription drug use trends among patients enrolled in New York state’s medical cannabis program yielded similar results. On average, subjects’ monthly analgesic prescription costs declined by 32 percent following enrollment, primarily due to a reduction in the use of opioid pills and fentanyl patches. “After three months treatment, medical cannabis improved [subjects’] quality of life, reduced pain and opioid use, and lead to cost savings,” authors concluded.
These conclusions are hardly unique. A study of 244 state-registered chronic pain patients enrolled in Michigan’s medical cannabis program reported: “[M]edical cannabis use was associated with a 64 percent decrease in opioid use, decreased number and side effects of medications, and an improved quality of life. This study suggests that many CP [chronic pain] patients are essentially substituting medical cannabis for opioids and other medications for CP treatment.”
A separate review of over 2,000 chronic pain patients in Minnesota reported that 63 percent of those who used opioids at the time of their admission into the program “were able to reduce or eliminate their opioid use after six months.”
Yet another study, this time evaluating the prescription drug use patterns of patients enrolled in Illinois’ medical access program, similarly revealed: “[O]ur results indicate that MC (medical cannabis) may be used intentionally to taper off prescription medications. These findings align with previous research that has reported substitution or alternative use of cannabis for prescription pain medications due to concerns regarding addiction and better side-effect and symptom management, as well as complementary use to help manage side-effects of prescription medication.”
Perhaps most notably, a 2017 study published in the journal PLoS ONE compared prescription drug use patterns among pain patients enrolled in the New Mexico medical access program versus similarly matched control patents who were not. Compared to non-users, over a 21-month period medical cannabis enrollees “were more likely either to reduce daily opioid prescription dosages between the beginning and end of the sample period (83.8 percent versus 44.8 percent) or to cease filling opioid prescriptions altogether (40.5 percent versus 3.4 percent).”
Of course, it would be silly to opine that cannabis legalization alone represents some sort of “silver bullet” in America’s ongoing battle against opioid abuse. Its potential role as an opioid-alternative in those patients suffering from chronic pain and other debilitating diseases must not be overlooked or altogether ignored.
Paul Armentano is the deputy director of NORML, the National Organization for the Reform of Marijuana Laws. He is the co-author of the book Marijuana Is Safer: So Why Are We Driving People to Drink?