Medical cannabis laws have negligible impact on opioid prescribing

State laws allowing medical cannabis use did not reduce prescriptions for opioids or other therapies for chronic, non-cancer pain, according to a policy analysis by Weill Cornell Medicine investigators.

Dr. Beth McGinty, chief of the Division of Health Policy and Economics at Weill Cornell Medicine, used a study design that emulates a clinical trial to analyze the effects of medical cannabis laws on treatment for people with chronic non-cancer pain. The results, published July 4 in Annals of Internal Medicine, challenge the results of previous studies that suggested medical cannabis laws might reduce opioid prescribing, helping curb the ongoing opioid crisis in the United States.

“Some research suggests that perhaps medical cannabis laws reduce opioid prescribing for chronic non-cancer pain because some people may substitute cannabis,” said Dr. McGinty, who was recruited as a professor of population health sciences 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.”

Public health authorities and policymakers hoping to stem the ongoing opioid overdose crisis in the United States have taken various approaches, including recommending more judicious opioid prescribing. Some have suggested allowing medical cannabis to give patients with chronic non-cancer pain an option with a lower risk of overdose. But many questions remain about this approach.

“The science is very much still evolving on how effective cannabis is for chronic non-cancer pain,” Dr. McGinty said. Questions remain about how effective cannabis is at treating chronic non cancer pain compared with evidence-backed therapies, including non-opioid pain medications and physical therapy.

To understand how medical cannabis laws affect chronic non-cancer pain treatment, Dr. McGinty and her colleagues used commercial insurance claims data to analyze opioid prescribing, non-opioid pain medication prescribing, and delivery of chronic non-cancer pain procedures like physical therapy in 12 states with medical cannabis laws and 17 states without such laws. The team used statistical adjustments to correct for any pre-law differences between pain treatment outcomes in medical cannabis states and their comparison states.  

“It’s an observational study, but we set it up in a way that mimics a clinical trial as closely as possible,” she said.

The study did not find a significant impact on the number of patients with chronic non-cancer pain receiving any prescription opioid, any non-opioid prescription pain medication, or on procedures used to relieve chronic pain. Dr. McGinty said the results were consistent across states with medical cannabis laws.

“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,” she said.

Dr. McGinty acknowledged that the study has limited statistical power, in part because there are only 50 states, a limitation in any study of the effects of state policies. Investigators could also examine the effects of medical cannabis laws on chronic pain treatment using a data source that captures medical cannabis use in addition to data on other chronic pain treatments, for example state prescription drug monitoring programs that are in some cases starting to include medical cannabis as well as opioid prescriptions.  

In the meantime, the study may provide valuable information for policymakers looking to understand how medical cannabis laws influence prescribing of prescription opioids and delivery of other treatments for chronic non-cancer pain.

“Our study findings suggest that medical cannabis laws do not significantly reduce opioid prescribing,” Dr. McGinty said. “Policy makers trying to curb excess opioid prescribing and overdoses should focus on other strategies.”