A new study finds a link between the legalization of medical marijuana and a reduction in the rate of opioid dispensing and pain-related hospital events in some cancer patients.

In a paper published in the journal JAMA Oncology, researchers look at insurance claims data from 2012 to 2017 for patients with breast, colorectal and lung cancers. Overall, they had data on nearly 60,000 patients between the ages of 18 and 64.

In 2012, there were 34 states where medical marijuana was not legalized. By 2017, 14 of them had implemented legalized medical marijuana. Another of the key changes was whether states allowed retail dispensaries, which increases availability and access.

For patients with lung cancer and recent access to opioids, medical marijuana legalization was associated with a reduction in pain-related hospital visits, from 19 to 13 percent. These reductions occurred soon after legalization.

For all types of cancer, the data also showed medical marijuana legalization was associated with a reduction in the rate of one or more days where the patient was in possession of prescription opioids during the first six months after diagnosis.

Medical marijuana legalization was associated with a 5 to 20 percent reduction in opioid dispensing after a new cancer diagnosis. Medical marijuana legalization accompanied by dispensary allowances was associated with a larger reduction in opioid dispensing compared with legalization without dispensaries.