MISSOULA — States like Montana that have passed laws legalizing medical marijuana have seen a decrease in traffic fatalities and a reduction in beer sales, a new study has found.
A report authored by D. Mark Anderson, a Montana State University economics professor, and Daniel Rees, a professor at the University of Colorado Denver, discovered a 9 percent decrease in traffic fatalities in states that passed laws legalizing medical marijuana. The study points to marijuana as a substitute drug for alcohol.
So far, 16 states have passed laws legalizing medical marijuana. Surveys show that residents in these states are reporting consuming less alcohol and retailers are reporting a 5 percent reduction in alcohol sales.
“That was really compelling,” Anderson said. “It’s data that either wasn’t analyzed or isn’t analyzed as frequently as it should be.”
Most of the data collected between 1990 and 2009 came from the National Survey on Drug Use and Health, the Behavioral Risk Factor Surveillance System and the Fatality Analysis Reporting System. The study includes the 13 states that had passed medical marijuana laws before 2009.
The study was posted on the Institute for the Study of Labor at the end of November.
The research idea came to Anderson a year ago as he watched medical marijuana dispensaries spring up along Grand Avenue in Billings and saw the issue in the news.
“It seems like there would be spillover effects that would affect more than just the card-carrying users,” he said. “With all the publicity that medical marijuana had been receiving, especially in states like Montana, it was hard to miss.”
A portion of the study examines alcohol consumption and marijuana consumption in three states: Montana, Rhode Island and Vermont. In Montana and Rhode Island, the authors found that the passage of laws legalizing medical marijuana led to increased marijuana use among adults in these states.
In Montana, marijuana use rose 19 percent among people ages 18-25 after medical marijuana was legalized.
While not all traffic fatalities are alcohol related, the study found that these kinds of traffic deaths decreased significantly. Traffic fatalities on the weekends and at night, when many alcohol-related traffic deaths occur, decreased after laws legalizing medical marijuana were passed, the study found.
In addition, the researchers found that beer sales in these states dipped 5 percent after medical marijuana was legalized.
Anderson recognizes that it’s possible that residents in these states are driving less. And the study doesn’t say that medical marijuana laws cause a drop in traffic fatalities.
Researchers also aren’t saying that smoking marijuana impairs drivers less than alcohol, but “it could be that,” Anderson said. “We’re saying our results would be consistent with that.”
The study has been receiving mixed reviews since it was first presented to the public. Not everyone agrees with its findings. The study is under review by the Journal of Law and Economics.
“We are hoping it will stimulate some kind of policy discussion beyond what’s discussed in the press,” Anderson said. “That’s the goal of doing this research. Hopefully when states decide whether to legalize medical marijuana or decide to go back on legalizing it, that this will be some research that will be included in the discussion.”