By Pat Anson, PNN Editor

The cannabis industry and advocates in the U.S. have long claimed that state laws legalizing medical marijuana could help solve the opioid crisis by reducing demand for prescription opioids.

Various studies have suggested that may be true, like a recent one in New York state that found patients on high-dose opioids significantly reduced their opioid use once they started using medical cannabis. A similar study in 2021 found that cannabis was so effective in reducing chronic pain that most patients were able to reduce or completely stop their use of opioids.

But a large new study of commercially insured adults with chronic non-cancer pain found that the legalization of medical cannabis in 12 states (Arkansas, Connecticut, Florida, Louisiana, Maryland, Minnesota, North Dakota, New Hampshire, New York, Oklahoma, Ohio, Pennsylvania) had little to no effect on opioid prescribing.  

“Some research suggests that perhaps medical cannabis laws reduce opioid prescribing for chronic non-cancer pain because some people may substitute cannabis,” said lead author Beth McGinty, PhD, chief of the Division of Health Policy and Economics at Weill Cornell Medicine. “We found no effects of these laws on opioid prescribing or any types of treatment for chronic non-cancer pain that we looked at.”

McGinty and her colleagues looked at prescription data for over 150,000 chronic pain patients in the four years prior to state legalization and compared it to their medication use in the three years after medical marijuana laws were adopted. That data was then compared to prescription data for over 430,000 pain patients in 17 other states without medical marijuana laws, who served as a control group   

The study findings, published in Annals of Internal Medicine, show that opioid prescribing for chronic pain fell only slightly in states with medical marijuana laws, leading to tiny decreases in the average supply of opioids (0.35 fewer days) and for daily doses in morphine milligram equivalents (0.42 less MME). Small reductions were also noted in the prescribing of non-opioid pain relievers and in treatments such as physical therapy.

Importantly, the decreases were not substantially different than the data from states where medical marijuana remained illegal.

“Medical cannabis laws do not appear to be associated with changes in the prescription opioid or other non-cannabis, non-opioid treatments for chronic non-cancer pain,” McGinty said. “Policy makers trying to curb excess opioid prescribing and overdoses should focus on other strategies.”

Researchers say the minimal impact of medical cannabis on opioid prescribing may be due to the slow implementation of medical marijuana laws. Surveys show that most doctors are reluctant to discuss cannabis with their patients, and have doubts about its safety and effectiveness.

Doctors may not approve, but nearly a third of U.S. adults with chronic pain have used cannabis as a pain reliever and over half of them have reduced their use of pain medication. Many had no choice but to look for alternatives. Nationwide, opioid prescribing for commercially insured adults has fallen by 51% since 2011.