Fewer Traffic Fatalities Occur in States with Medical Marijuana Laws, Study Finds

By Zachary Siegel 01/04/17

The steepest reduction in traffic deaths was found among drivers aged 25 to 44. 

Cars sitting in traffic.

States where it’s legal to use cannabis medicinally have fewer traffic fatalities than states without medical marijuana laws, according to a new study published in the American Journal of Public Health

On average, states that passed medical marijuana laws saw an 11% reduction in traffic fatalities after enacting the laws, and also had 26% lower rates of traffic fatalities compared with states without the laws. 

The group that saw the steepest reduction in traffic deaths was among those aged 25 to 44 years old, which is particularly striking given that this group represents a high percentage of medical marijuana patients. 

Conducted by epidemiologists at Columbia University’s Mailman School of Public Health, this study complicates prior research that shows cannabis causes impaired driving as a result of decreased reaction time and poor motor coordination. But this study does not show that driving high isn’t dangerous. Rather, it points to a relationship between medical cannabis laws and a reduction in traffic fatalities. 

There are several explanations as to why this relationship was found. For one, “states with medical marijuana laws and lower traffic fatality rates may be related to lower levels of alcohol-impaired driving behavior in these states,” Silvia Martins, MD, PhD, associate professor at the Mailman School and senior author, said in a statement.  

“We found evidence that states with the marijuana laws in place compared with those which did not, reported, on average, lower rates of drivers endorsing driving after having too many drinks.” 

Dr. Martins is implying what other studies have found, which is that drinking and driving is more dangerous than driving with a cannabis buzz. 

Medical marijuana laws aside, the presence of dispensaries were also associated with a significant reduction in traffic fatalities in those aged 25 to 44 years. This finding could be a thorn in the side of those who have argued to shutter cannabis dispensaries, citing potential dangers. 

While the study found an overall reduction in traffic fatalities, some states with medical marijuana laws did show increases. 

After enacting medical marijuana laws, both California and New Mexico saw reductions in traffic fatalities by 16 and 17.5%, respectively. But over time the laws in California and New Mexico were associated with gradual increases in fatality rates. The authors say that the state-specific differences show the need for future research. 

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Zachary Siegel is a freelance journalist specializing in science, health and drug policy. His reporting has also appeared in Slate, The Daily Beast, Salon, Huffington Post, among others. He writes often about addiction, sometimes drawing from his own experience. You can find out more about Zachary on Linkedin or follow him on Twitter.