States which had legalized marijuana use for medicinal purposes saw a combined drop of $165.2 million in Medicare Part D spending in 2013, according to a new study published in Health Affairs.

Authored by Ashley Bradford, a master of public administration student at the University of Georgia, the study is said to be the first of its kind to address whether clinical practices are changed when medical marijuana is legalized, and whether it could lower public health costs.

The report sought to answer two questions: Does having a medical marijuana law change prescribing patterns in Medicare Part D for traditional, FDA-approved drugs that treat the same conditions as marijuana? If it does, what is the effect on Medicare and out-of-pocket spending?

Using Part D data from 2010 to 2013, the answer to the first question appears to be yes.

“With the exception of glaucoma, fewer prescriptions were written for any of our study condition categories when a medical marijuana law was in effect,” Bradford wrote. “When we controlled for other factors that might have been driving differences in prescribing across states that did and did not have medical marijuana law in effect, we found similar results.”

Besides glaucoma, the conditions analyzed were anxiety, depression, nausea, pain, psychosis, seizures, sleep disorders and spasticity.

For seven of those categories—all but glaucoma and spasticity—medical marijuana laws led to physicians filling fewer prescriptions. The pain category saw the biggest drop, with 1,826 fewer daily doses filled annually per physician.

Bradford also looked at prescribing patterns for conditions which can’t be treated by marijuana, like blood-thinners or antibiotics, and found no change after a medical marijuana program was implemented.

“This provides strong evidence that the observed shifts in prescribing patterns were in fact due to the passage of the medical marijuana laws,” Bradford wrote.

As for its effect on spending, the study estimated the savings related to the reduced number of prescriptions totaled almost $165.2 million in 2013 in the 17 states and the District of Columbia which had legalized medical marijuana by that time. Had all states adopted such a law by 2013, the study estimates Medicare Part D spending would’ve dropped by $468.1 million when compared to models where no states had legalized medical cannabis.

“At a time when Medicare is under increased fiscal pressure, our research suggests that more widespread state approval of medical marijuana could provide modest budgetary relief,” Bradford wrote. “Although some of the savings are likely to be a transfer of costs from the Medicare program to beneficiaries who would have purchased marijuana out of pocket, saving $468.1 million annually is not trivial.”

Since 2013, nine additional states have implemented medical marijuana laws. Florida and Arkansas may join them if voters approve statewide referendums on medical marijuana on their November ballots, with the inclusion of a Missouri initiative still pending.