MASSACHUSETTS: As legal marijuana spreads across America, mostly for medical use, anxiety about its side effects is spreading with it: What other changes will it bring? Campaigns against loosening the law tend to focus on its unknown and possibly dangerous repercussions—a surge in pot smoking, perhaps opening the door to increased use of harder drugs and to associated spikes in crime and other societal ills.
Amid the heated debate, a small amount of hard data is starting to emerge. And among the most intriguing findings is a recent study suggesting that Massachusetts could enjoy an unexpected boon from last November’s vote to legalize medical marijuana: fewer deaths on our roads and highways.
A team of economists who specialize in health and risk behaviors looked at the link between marijuana laws and traffic deaths, and found that roadway fatalities dropped significantly in states after they legalized medical marijuana. On average, deaths dropped 8 to 11 percent in the first full year after the law went into effect, and fell 10 to 13 percent by year four. Five years out, the results grew more varied, and faded in some cases.
The study doesn’t include Massachusetts, whose medical-marijuana law just went into effect in May, well after the researchers had finished collecting and analyzing their data. But applied to Massachusetts’ most recent traffic fatality statistics, the study’s findings would roughly translate to about 35 lives saved per year.
The notion that loosening the restrictions on a drug—one that’s hardly known for improving reaction times—might actually improve traffic safety is surprising on the face of it, and the researchers are careful to say that there’s nothing safe about driving under the influence of marijuana. But as they try to unpack what might be making the difference, it is becoming clear that the knowledge emerging from America’s new experiments with marijuana law could significantly change the public conversation—giving us new data about the effects of drugs on society, and landing a familiar debate on unfamiliar new ground.