Medical Marijuana DispensaryA new study finds fewer traffic deaths in states that have legalized medical marijuana, theorizing that in those states, some people are substituting marijuana for alcohol, at least some of the time.

The study was done by University of Colorado Denver professor Daniel I. Rees and Montana State University professor D. Mark Anderson, and is posted on the website of the Germany-based Institute for the Study of Labor. It has not yet been peer-reviewed.

The researchers looked at National Highway Traffic Safety Administration data for the 15 states (plus the District of Columbia) that have legalized medical marijuana use since 1996. By comparing the information from before and after passage of those laws, the study found a nearly 9% decrease in overall traffic fatalities after medical marijuana was legalized. And as Christopher Shea reports on The Wall Street Journal blog Ideas Market, researchers also noted trends in neighboring states. The study found that the decline in fatalities was caused almost entirely by the drop in alcohol-related deaths.

As John Ingold writes in the Denver Post, the study found that legalization of medical marijuana is associated with a 12% drop in the alcohol-related fatal-crash rate and a 19% decrease in the fatality rate of people in their 20s.

Shea writes on the blog Ideas Market:

In states that have legalized medical marijuana, the researchers found evidence of an increase in marijuana consumption — beyond prescription uses — among people over 18 (but not under 18).* According to their analysis of data collected by the Centers of Disease Control and the states, those states have also seen a slight drop in alcohol consumption. Taken as a whole, the data suggest that marijuana is being used as a partial replacement for drinking, and not only a supplement to drinking.

Like alcohol, marijuana hinders physical coordination. People who are high, however, tend to be more aware of their intoxication, and less aggressive and reckless, than people who are drunk, the researchers said. Another factor in the fatality drop may be that people consume marijuana in private, rather than in bars (or sports stadiums) they drive home from.

Source: ‘Medical Marijuana Laws, Traffic Fatalities, and Alcohol Consumption,’ D. Mark Anderson and Daniel I. Rees, Institute for the Study of Labor working paper (November)

*That medical-marijuana laws lead to more marijuana use among adults was the general trend, but it wasn’t universal. Montana, where nearly 3% of the population has a marijuana prescription (!), and Rhode Island, where only some 3,000 people do, both saw increases in pot consumption. Vermont, however, with a medical-marijuana patient roster measured in the hundreds, did not see an increase in pot consumption

As Ingold writes, this study is certain to exacerbate the debate about the effect of Colorado’s medical marijuana “boom” on traffic safety:

The state legislature this year rejected a bill that would have set a threshold of THC — the psychoactive chemical in marijuana — that would qualify someone as too stoned to drive. After more research and a fractious debate, the Colorado Commission on Criminal and Juvenile Justice will not recommend that the legislature try again with such a bill this year. […]

Much of that debate has focused on marijuana’s impact on an individual’s driving abilities. Rees and Anderson say their study does not mean it is safer to drive stoned than drunk. Instead, they write, increased medical-marijuana usage at home might change patterns of substance use and driving.

Image by Goodnight London (Dominick Simpson), used under its Creative Commons license.

Embed this infographic:
Embed this image: