NEW YORK (MainStreet) — As it turns out, states where medical marijuana is legal are reaping one big benefit: lower death rates from opioid drugs. This is according to a new multi-institutional study conducted at the Perelman School of Medicine at the University of Pennsylvania and recently published in JAMA Internal Medicine

For the study--which was supported by the National Institutes of Health, the Center for AIDS Research at the Albert Einstein College of Medicine and Montefiore Medical Center -- the researchers analyzed death rates related to opioid overdoses that occurred between 1999 and 2010.

The findings revealed that mortality rates from opioid overdoses were cut by nearly a quarter (24.8%) in those 13 states where medical marijuana was legal during that timeframe. The study also found that the relationship between lower opioid-related deaths and the existence of medical marijuana laws increased over time. Specifically, casualties related to opioid overdose in a given state decreased by an average of 20 percent in the first year after medical marijuana was legalized and then 33.7% after five years.

"[Medical cannabis] may provide relief for some individuals," said Marcus A. Bachhuber, MD, Robert Wood Johnson Foundation Clinical Scholar at Penn and the Philadelphia VA Medical Center and lead author of the study. "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."

Opioid analgesics, which include OxyContin, Percocet and Vicodin, are often prescribed to patients who suffer moderate to severe pain. These drugs work by suppressing the perception of pain by dulling pain receptors in the brain. In the past decade, the number of patients prescribed opioids for non-cancer pain has doubled in the United States. In fact, in nearly 60% of the cases of fatal opioid overdose, the patient has a valid prescription.

The study has even more dire implications for women. As noted by Chelsea Rice of the Boston Globe, more women have died each year from overdoses than from motor vehicle-related injuries since 2007.

Meanwhile, overdosing on marijuana is virtually unheard of in the medical community.

"There are simply no deaths--zero--attributable to marijuana, according to the government's own statistics, from the federal Centers for Disease Control and Prevention, as well as from other studies," writes health journalist Judy Foreman in her book A Nation in Pain.

Foreman explains that this is because unlike opioids, marijuana does not cause respiratory depression. Yet, some studies indicate marijuana can be as effective opioids in treating pain and work much the same way.

"[Marijuana] can reduce chronic pain more than 30%, and with fewer serious side effects," writes Foreman, who also notes in her book that marijuana has fared very well in multiple double-blind placebo studies.

Anecdotally, many patients seem to concur with Foreman's observations and believe medical marijuana to be just as effective (if not more) for their pain as opioids, while causing less side effects.

"I lived off of opioids for almost three years [and] found they were doing more harm than good," says Laura, 25, from Canada, where medical marijuana is legal. "They actually caused more issues, and I found my pain getting worse with use of them. Not to mention, I was using so many a day that I could hardly function. Medical marijuana is much better [and] my pain has substantially decreased with its use."

Originally, Laura (who asked that he last name be withheld) was opposed to the idea of taking medical marijuana for her health condition, because she viewed it as a dangerous drug, a perception that was reinforced by the fact that her prescription plan does not cover it.

Since insurance plans generally do not cover medical marijuana, and the cost of a doctor's assessment and recommendation can often be steep -- between $150 and $200 in the state of Massachusetts --this can pose a challenge to patients in gaining access.

"[P]erhaps the biggest hurdle for insurers is the U.S. Food and Drug Administration hasn't approved it," wrote Tom Murphy of medical marijuana for the Associated Press back in May. "Major insurers generally don't cover treatments that are not approved by the FDA, and that approval depends on big clinical studies that measure safety, effectiveness and side effects."

Since marijuana is has Schedule I classification under the federal Controlled Substances Act, it can be difficult to conduct clinical studies that support its effectiveness as a remedy for pain, despite compelling anecdotal evidence.

"I can call up my doctor any time for an opioid prescription and for the cost of a prescription copay I can pick it up today," says Julie, 38, of Somerville, Mass, who also asked that her last name be withheld. "The cost of a medical marijuana prescription is completely out of the question for my budget, never mind the cost of the medical marijuana itself. Marijuana and opioids have about equal effectiveness for me, but [marijuana] has no side effects while opioids make me sick to my stomach."

As of the end of June, 23 states in the U.S. have legalized cannabis for medical use.

--Written by Laura Kiesel for MainStreet