A new study revealed states that allow medical marijuana tend to have fewer painkiller-related deaths.

Opioid analgesics, such as Vicodin, Percocet, and OxyContin, are often prescribed for moderate to severe pain. Researchers reviewed the rate of deaths caused by opioid overdoses between 1999 and 2010 and found states that allow the use of medical marijuana had a 24.8 percent lower annual opioid overdose mortality rate after the laws were enacted, the University of Pennsylvania School of Medicine reported.

About 60 percent of all opioid overdoses occur in individuals who have legitimate prescriptions. The number of patients in the U.S. who are prescribed opioids for non-cancer pain has almost doubled over the past decade. In states that allow it, medical marijuana can be used in replace of these drugs.

 "It may provide relief for some individuals," said lead author, Marcus A. Bachhuber, MD, Robert Wood Johnson Foundation Clinical Scholar at Penn and the Philadelphia VA Medical Center. "In addition, people already taking opioids for pain may supplement with medical marijuana and be able to lower their painkiller dose, thus lowering their risk of overdose.

The study also found relationship between lower opioid overdose deaths and medical marijuana laws strengthened over time. Painkiller-related deaths were about 20 percent lower a year after the laws were passed and 33.7 percent lower five years after the laws were implemented.

While replacing opioids with medical marijuana could be partially responsible for the drop in deaths, the substance could also change the way people misuse or abuse pain killers. This could occur because both marijuana and opioids stimulate similar areas of the brain's pathways. The researchers hope to gain more insight into this phenomenon as well as the link between marijuana use and opiate abuse in future studies.

The findings were published in JAMA Internal Medicine