Prescriptions for the painkilling opioid codeine have decreased in states that have legalized marijuana, according to a study published in the research journal Health Economics.
The study, published on Jan. 18 by researchers from Cornell University, George Mason University, the University of Georgia and the University of Pittsburgh, drew on data analyzing opioid shipments from 11 states that have legalized cannabis for adult use.
The study period was between 2010 and 2019 and compared legal marijuana states with those that still outlaw the federally illegal, Schedule I drug.
The researchers stated that their study examined the impact of legal recreational marijuana on prescription opioid dispensing across all payers and endpoints, including pharmacies, hospitals and specialists.
The study took into account factors such as opioid prescribing limits, and it addressed opioids of various types including codeine.
They determined that states that legalized recreational cannabis use have seen around a 26% reduction in the amount of codeine dispensed at retail pharmacies, and that the findings are “potentially promising from a public health perspective.”
Codeine, the researchers said, is one class of opioid that appears to be used non-medically as compared with other prescription opioids.
The team said that their study differs from previous studies that have looked at recreational marijuana laws and how they affect opioid prescriptions financed by private and public payers or dispensed to unique endpoints.
According to the researchers, a total of 21 states have now legalized marijuana recreationally.
Thirty-seven states, including Washington, D.C., have medical cannabis programs, according to the National Organization for the Reform of Marijuana Laws.