The legalization of medical marijuana in the United States is associated with reductions in opioid dispensing and pain-related hospital visits in patients with cancer, according to researchers.
They cautioned, however, that these associations need to be investigated further. The findings were published in JAMA Oncology.
The researchers analyzed national commercial claims data from 2012 to 2017 to examine whether medical marijuana legalization is associated with opioid use or pain outcomes in adults receiving cancer treatment.
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The cohort included 38,189 patients with breast cancer, 12,816 patients with colorectal cancer, and 7190 patients with lung cancer.
The researchers looked at a few outcomes, including having 1 or more days of opioid use, 1 or more days of long-acting opioid use, total morphine mg equivalent of any opioid dispensed to patients with 1 or more opioid days, and 1 or more pain-related emergency department visit or hospitalization during the 6 months after a new cancer diagnosis.
The legalization of medical marijuana was associated with a significant reduction in the rate of 1 or more opioid days across cancer types. For breast cancer patients with recent opioid use, the rate decreased from 90.1% to 84.4% (P =.001).
For colorectal cancer patients with recent opioid use, the rate of 1 or more opioid days decreased from 89.4% to 84.4% (P =.03). For lung cancer patients without recent opioid use, the rate decreased from 33.8% to 27.2% (P =.02).
Among patients with lung cancer who had recent opioid use, the legalization of medical marijuana was associated with a reduction in the rate of 1 or more long-acting opioid days from 31.5% to 22.1% (P =.03). Medical marijuana legalization was also associated with a reduction in the rate of 1 or more pain-related hospital events from 19.3% to 13.0% (P =.03).
The researchers suggested several possible mechanisms for these associations.
“Legal access to medical marijuana may have led oncologists and other practitioners to prescribe fewer opioids,” the researchers wrote. “Medical marijuana legalization may also have been associated with lower demand for opioids by patients who use marijuana when self-managing pain as well as by those who were reluctant to complain about pain when perceiving marijuana as an alternative to opioids.”
Additional studies are needed to “investigate the nature of the associations to shed light on causal mechanisms,” the researchers concluded.
Disclosures: This research was supported by Arnold Ventures. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.
Reference
Bao Y, Zhang H, Bruera E, et al. Medical marijuana legalization and opioid- and pain-related outcomes among patients newly diagnosed with cancer receiving anticancer treatment. JAMA Oncol. Published online December 1, 2022. doi:10.1001/jamaoncol.2022.5623
