Prescribing Cannabis to Treat Opioid Addiction is Irresponsible and Unscientific, Say Experts

Prescribing Cannabis to Treat Opioid Addiction is Irresponsible and Unscientific, Say Experts

New York and Illinois recently revised their medical marijuana laws to allow medical cannabis as a substitute for opioids for chronic pain and addiction. Pennsylvania has also approved cannabis to help wean patients off opioids, and more states are looking at it. The cannabis-for-opioid-use-disorder conversation is heating up, but not everyone agrees.

Replacing opioids with cannabis for treating chronic pain is poorly supported by evidence, say two leading addiction experts. And using cannabis for opioid addiction treatment is even worse, it's potentially harmful, they say.

"The suggestion that patients should self-substitute a drug (i.e., cannabis) that has not been subjected to a single clinical trial for opioid addiction, is irresponsible and should be reconsidered," write Keith Humphreys, PhD, a behavioral sciences professor at Stanford University, and Richard Saitz, MD, head of the community health sciences department at Boston University School of Public Health.

"There are no randomized clinical trials of substituting cannabis for opioids in patients taking or misusing opioids for treatment of pain, or in patients with opioid addiction treated with methadone or buprenorphine," they said.

Writing in the Network edition of the Journal of the American Medical Association, Humphreys and Saitz point out that recent systematic reviews "have identified low-strength evidence that plant-based cannabis preparations alleviate neuropathic pain."

But there is insufficient evidence for other types of pain, they say. "Studies tend to be of low methodological quality, involve small samples and short-follow-up periods, and do not address the most common causes of pain, for example, back pain."

Questioning addiction treatment

When it comes to opioid addiction treatment, much more work needs to be done to accurately determine suitability and effectiveness.

"The evidence that cannabis is an efficacious treatment for opioid use disorder is even weaker," the article says. "To date, no prospective evidence, either from clinical trials or observational studies, has demonstrated any benefit of treating patients who have opioid addiction with cannabis."

Most of the motivation for supporting cannabis to combat opioid addiction is derived from population-level data that suggest fewer opioid overdose deaths occur in areas with legalized marijuana. But that evidence is slim, and in some areas, the opposite is actually the case, say Humphreys and Saitz.

"In addition to surveys of patients who use medical cannabis, the other types of studies prompting a move to cannabis to replace opioids are population-level reports stating that laws allowing medical cannabis use are followed by fewer opioid overdose deaths than expected."

A major problem with such studies is flawed methodology, which evokes the standard observation that "correlation is not causation."

"Many factors other than cannabis use may affect opioid overdose deaths, such as prescribing guidelines, opioid rescheduling, Good Samaritan laws, incarceration practices, and availability of evidence-based opioid use disorder treatment and naloxone," they write. "Furthermore, the aggregate population associations between medical cannabis and opioid overdose may be opposite of those seen within individuals."

Study shows more opioid use and abuse, not less

The only individual-level study that looked at personal-level relationships between cannabis and opioid use was published last summer in the Journal of Addiction Medicine. Humphreys was an author of that study, along with T. L. Caputi from the School of Public Health at Ireland's University College Cork.

Unlike the broad, population-based, scientifically weak surveys supporting cannabis use, this first-of-its-kind study conclusively shows that medical marijuana users not only used significantly more prescription drugs medically, they were significantly more likely to use prescription drugs non-medically, including elevated risks for non-medical use of pain relievers (opioids), stimulants (cocaine, meth) and tranquilizers (benzos).

These results must be disappointing to cannabis supporters, but they are nevertheless irrefutable. Cannabis use is positively associated with greater use and misuse of prescription opioids.

"Medical marijuana users should be a target population in efforts to combat nonmedical prescription drug use," Humphreys wrote.

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