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January 20, 2016

Legal, Policy Changes Can Lead to Shifts in Use of Medical Marijuana

Use increased in states with dispensaries after 2009 federal policy change; changes in state laws saw varying responses

A Johns Hopkins Bloomberg School of Public Health analysis of registered medical marijuana users found that a hodgepodge of law and policy changes since 2001 had varying effects on the number of people consuming what in many states remains an otherwise illegal drug for its purported health benefits.

The findings, published online in the journal Drug and Alcohol Dependence, suggest a possible “participation elasticity” that could inform future discussions around medical marijuana provisions at both the state and federal level. Medical marijuana is legal to varying degrees in 23 states and the District of Columbia. 

In one finding, researchers determined that medical marijuana use in the states of Colorado, Montana and Michigan rose dramatically in 2009 when the federal government announced that it was making medical marijuana prosecutions a low priority. (In the previous administration, the federal government prosecuted medical marijuana users along with recreational users, since marijuana was -- as it is today -- against federal law.) By contrast, medical marijuana participation rose little in states the expressly prohibited dispensaries, such as Alaska, Rhode Island and Vermont.

The federal policy change led to an increase in the number of medical marijuana dispensaries, which may have led to an increase in medical marijuana participation. When Colorado and Montana responded with regulations aimed at limiting dispensaries, their numbers fell, as did the number of medical marijuana registrants in these states.

“At one point, it seemed like there were more dispensaries than Starbucks in some cities,” says study author Brian Fairman, PhD, a postdoctoral fellow in the Bloomberg School’s Department of Mental Health. “Then when the number of dispensaries dropped, so did the number of registrants. Interestingly, after Colorado legalized recreational marijuana use, the rates of medical marijuana participation held steady, perhaps because sales taxes are lower for medical marijuana, so it’s more affordable.”

California became the first state to allow medical marijuana use in 1996. Since then, another 22 states and the District of Columbia approved medical marijuana use. An estimated 2.7 million people use medical marijuana, according to data based on a household survey from the U.S. National Survey on Drug Use and Health. However, state registries log only about 440,000 medical marijuana users, in part because registration is voluntary in some states, including California, so many patients do not register.

The rules governing the practice currently vary from state to state, with some allowing dispensaries and some not, and two states, New York and Minnesota, prohibiting cannabis that is smoked (but allowing ingestion and vaporizing). Most patients who use medical marijuana do so for pain relief.

For this analysis, only 13 states, along with the District of Columbia, with medical marijuana registries that had data available over time were included. The states analyzed were Alaska, Arizona, Colorado, Connecticut, Hawaii, Michigan, Montana, Nevada, New Jersey, New Mexico, Oregon, Rhode Island and Vermont.

Other findings include:

The benefits of medical marijuana are little understood, largely because there is scant research, which is complicated by required clearance from the U.S. Drug Enforcement Administration.

“Marijuana policy is at a crossroads,” Fairman says. “It’s especially important that policymakers and the public understand what might contribute to trends in medical marijuana use, considering the number of people who seek it for chronic pain and also how it might interplay with recreational use as more states legalize recreational marijuana.”

Trends in registered medical marijuana participation across 13 U.S. states and District of Columbia” was written by Brian J. Fairman, PhD.

The author acknowledges funding support by the National Institutes of Health under the Ruth L. Kirschstein National Research Service Award (T32DA007292) from the National Institute on Drug Abuse.

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Media contacts for the Johns Hopkins Bloomberg School of Public Health: Barbara Benham at 410-614-6029 or and  Stephanie Desmon at 410-955-7619 or