Check Up: Study: Medical pot may help lower deaths from painkillers

A new analysis suggests that states that legalized marijuana for pain relief may have averted some deaths from more dangerous painkillers - prescription opioids.

But the study also found that states with medical marijuana laws consistently had higher opioid death rates than states without such laws, showing the complexity of this country's opioid crisis.

"States that passed these laws are different than states that didn't pass laws," said lead author Marcus A. Bachhuber, an internal medicine fellow at the Philadelphia VA Medical Center. "They might have different patterns of chronic pain, or opioid prescribing, or drug use, and so on."

Abuse and diversion of highly addictive opioid painkillers such as OxyContin, Percocet, and Vicodin have become a lethal scourge, surpassing vehicle crashes as a cause of accidental deaths in many states, studies show. About 17,000 overdose deaths in 2011 involved the prescription painkillers, far more than cocaine and heroin combined, according to federal data.

Many states, including New Jersey, have adopted prescription-drug monitoring to reduce the problem, although a bill to create such a system has languished in Pennsylvania.

Bachhuber and his colleagues from the University of Pennsylvania and Johns Hopkins University wondered whether non-opioid pain treatment could help. They speculated that patients might reduce opiate use if they could get marijuana, which can be prescribed for pain in all states that permit medical use. (As of July, 23 states, including New Jersey, had such laws; a bill has been introduced in Pennsylvania.)

Some research suggests that marijuana increases substance abuse by serving as a "gateway" or "stepping-stone" drug, so the researchers' hunch was just that.

Their analysis, published last week in JAMA Internal Medicine, used federal data on opioid overdose deaths between 1999 and 2010. They compared mortality rates in the 13 states that have medical marijuana laws with rates in the other 37 states.

Although the trend was upward in both groups, states with medical marijuana laws had higher opioid death rates. In 2010, the death rate per 100,000 residents was 7.1 in states with laws, and 6.5 in states without.

To pinpoint the laws' impact and eliminate the effects of variables such as prescription- monitoring programs, the researchers made various mathematical adjustments.

The result was that, over the decade, the laws were linked to an average 25 percent lower annual death rate. In 2010 alone, this translated to 1,729 fewer overdose deaths than would have been expected if the laws didn't exist.

This beneficial impact persisted even when the researchers excluded intentional overdoses - that is, suicides - and included heroin overdose deaths that did not clearly involve opioids.

"The main critique of studies like this is that it's not a controlled experiment," Bachhuber said. "You're looking at information and using statistical models. I would just say that we looked at it in many different ways, and the effect on death rates was robust."

But the study hints at the complex economic and social problems that go hand-in-hand with opioid abuse. In 2010, the 13 states with medical marijuana laws were overwhelmingly rural. The rural poor, Medicaid patients, and people with psychiatric illness are at high risk of opioid overdose, studies have found.

"People living in rural poverty often work in very dangerous jobs where chronic pain at a young age is common," said Marie J. Hayes, a University of Maine psychologist who studies prenatal opiate exposure. "We see that here in Maine - people working in the woods or on the water. And if they can't work [because of job-related disability], they have the tremendous stress of poverty and the lack of a place in society."

In an editorial accompanying the new study, Hayes doubted that the modeled reduction in opioid death rates was due to improved pain control with marijuana. Rather, she said, cannabis "may lessen the drive to use opiates at lethal levels in people with nonpain, psychiatric conditions."

In any case, she wrote, "the potential protective role of medical marijuana . . . and its implication for public policy is a fruitful area for future work."