Medical marijuana laws had little impact on curbing non-medical use of prescription opioids, according to a new study that raises doubts over legal marijuana as an alternative to current substance use disorder treatments.
Non-medical use of prescription opioids slightly increased in states with medical marijuana laws, the study published Wednesday in JAMA Network Open found. Researchers analyzed substance use behavioral data from more than 672,000 individuals ages 12 and older from 2004 to 2012.
Medical marijuana supporters have argued the drug could be a substitute pain treatment in lieu of opioids, thereby lowering patients' risk of developing substance use disorder or dying from an overdose. That argument gained more attention after a 2014 study published in JAMA Internal Medicine found states with medical marijuana laws between 1999 and 2010 had a nearly 25% lower annual average rate in opioid overdose mortality compared with states without such laws.
But subsequent studies haven't supported the theory. One study published in June in the Proceedings of the National Academies of Science that replicated the 2014 study found states with medical marijuana laws saw more deaths from opioid overdose than states without such statutes if they included data up to 2017.
"With our data, we found very little evidence of an association between the enactment of these laws and the misuse or opioid use disorder among people who use opioids," said study co-author Dr. Silvia Martins, director of the substance abuse epidemiology unit at Columbia University's Mailman School of Public Health.
Martins said environmental factors mostly likely had a greater impact on opioid-related harm outcomes, such as the kind of drug policies states may have implemented. Other factors, such as the proliferation of more powerful synthetic opioids like fentanyl may have also had an impact.
Martins said more research was needed to better understand whether marijuana or any of its compounds are an effective chronic pain alternative treatment to opioids or a possible harm reduction therapy to help wean individuals off their opioid dependence.
Yet the lack of clinical evidence has not stopped a number of private drug treatment centers from offering cannabis as a form of opioid-addiction therapy, either to curb cravings or mitigate withdrawal symptoms.
The movement to make cannabis a viable opioid use disorder treatment has carried over to several states. Since 2017, three states — New Jersey, New York and Pennsylvania — have included opioid use disorder as a qualifying medical condition for cannabis.
At least 12 states have passed or are considering bills to allow medical marijuana or cannabidiol as an opioid treatment, according to the Association of State and Territorial Health Officials.
"It would be dangerous if people used it as a standard treatment in the absence of evidence," said Dr. Peter Grinspoon, an instructor of medicine at Harvard Medical School and a member of the board of directors for the advocacy group Doctors For Cannabis Regulation. "But I wouldn't be surprised in the future — just given how many people say it works for them — if it turns out to be a treatment."
While the evidence doesn't support using cannabis as a primary medication-assisted treatment like methadone or buprenorphine, Grinspoon claimed patients who used marijuana as such reported positive outcomes.
But he contended the debate over whether marijuana should or could be used to help treat opioid use disorder is complex, as most individuals experiencing opioid addiction don't have access to standard treatment medications.
In 2016, roughly 20% of the 2.1 million Americans estimated to have an opioid use disorder obtained specialty treatment, according to the U.S. Substance Abuse and Mental Health Services Administration. Only 37% of those receiving treatment got medication-assisted treatment.
"Great can be an enemy of the good," Grinspoon said. "Is nothing better than something that might work?"
But with no evidence of its efficacy, there are still too many unanswered questions about cannabis that lead to safety concerns, according to Dr. Melissa Weimer, a member of the American Society of Addiction Medicine's board of directors.
In January, the organization's New York chapter sent a letter to New York State Health Commissioner Dr. Howard Zucker urging him to remove opioid use disorder from the list of medical conditions that are eligible for cannabis over concerns that the regulation created "a dangerous public health message".
"I think that it's detracting from other efforts which could improve access to other lifesaving, evidence-based treatments," Weimer said. "I would rather have seen public health agencies focus effort on that rather than expend energy and time detracting from those evidence-based options."