Legalization of medical marijuana is associated with a reduction in opioid dispensing and pain-related hospital events among adults receiving treatment for newly diagnosed cancers, according to a study published online Dec. 1 in JAMA Oncology.

Yuhua Bao, Ph.D., from Weill Cornell Medicine in New York City, and colleagues conducted a crosssectional study using 2012 to 2017 national commercial claims data and a difference-in-differences design to examine the association between medical marijuana legalization that took effect between 2012 and 2017 and opioid-related and pain-related outcomes for patients receiving cancer treatment. Data were included for 38,189 patients newly diagnosed with breast cancer (100 percent women); 12,816 with colorectal cancer (55.4 percent men); and 7,190 with lung cancer (51.1 percent women).

The researchers found that medical marijuana legalization was associated with a reduction in the rate of one or more opioid days among patients with breast cancer with recent opioids, with colorectal cancer with recent opioids, and with lung cancer without recent opioids (difference, 5.6, 4.9, and 6.5 percentage points, respectively). Among patients with lung cancer with recent opioids, legalization of medical marijuana was associated with a reduction in the rate of one or more pain-related hospital events (difference, 6.3 percentage points).

“The findings suggest that medical marijuana could be serving as a substitute for opioids to some extent,” the authors write. “Future studies need to elucidate the nature of the associations and their implications for patient outcomes.”