Among adults receiving treatment for newly diagnosed cancer, medical marijuana legalization was associated with less opioid prescription and fewer pain-related hospital visits, according to study findings published in JAMA Oncology.

“Medical marijuana could be serving as a substitute for opioid therapies among some adult patients receiving cancer treatment,” the researchers concluded.

To date, 38 states and Washington, DC, have legalized cannabis, with about half of them allowing only medical use and half permitting both medical and recreational use. Marijuana is often used medicinally to improve appetite, reduce nausea and relieve pain. Studies have shown that cannabis helps reduce pain among people with cancer. A 2017 survey found that one in five cancer patients had used marijuana during the past year, but this has likely risen as more states have made it legal.

Yuhua Bao, PhD, of Weill Cornell Medicine in New York City, and colleagues conducted a study to see whether medical marijuana legalization was linked to changes in cannabis and opioid use among cancer patients.

For the study, the researchers accessed national commercial insurance claims data from 2012 through 2017. During this period, about a dozen additional states legalized medical marijuana. What’s more, retail cannabis dispensaries became more common, thereby increasing access.

The cross-sectional study included 38,189 people who were recently diagnosed with breast cancer, 12,816 with colorectal cancer and 7,190 with lung cancer. All participants were between the ages of 18 and 64, had private insurance and began treatment within six months of receiving their diagnosis.

Across all cancer types, medical marijuana legalization was linked to a decrease in opioid use. Opioid dispensing decreased by 5% to 20%, depending on the type of cancer, after legalization; states that allowed dispensaries saw a larger reduction. Emergency visits and hospitalization due to pain fell from 19% to 13% among people with lung cancer who had recently used opioids, and to a lesser extent among breast cancer patients, soon after legalization.

These findings “reinforce the importance for clinicians to ask patients what they are using to manage cancer-related pain, to discuss benefits and risks, and to address potential harm associated with drug interactions, polysubstance use and use of products for which scientific evidence, clinical guidelines, and government regulations are lacking,” the study authors wrote. “Frontline medical marijuana dispensary staff likely play an important role in mitigating adverse outcomes. Understanding and improving the quality of their counseling and communication practices will be another area of critical importance.”

Click here to read the study in JAMA Oncology.

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