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.