One study found high drivers drove slower, with longer following distances.
We all know drinking and driving is wrong, but what about smoking marijuana and driving? That’s also thought to be a no-no. In fact, the Centers for Disease Control and Prevention (CDC) says that driving while high on weed can distort perception and impair coordination, leading to slow reaction times and difficulty making decisions while behind the wheel.1
But in the wake of Canada legalizing marijuana use in 20182 and 19 states in the U.S., plus Washington, D.C.3 doing so as well, there is a growing fear more people will ingest marijuana and fire up the ignition, causing more accidents, injuries, and deaths. But how does THC (the psychoactive ingredient in marijuana) really affect driving ability? Is driving high really driving under the influence?
Several studies over the years from organizations like the National Institute on Drug Abuse have found a correlation between marijuana use and an uptick in at-fault accidents.4 CDC data has supported this conclusion as well.
However, a new report from the Canadian Institute of Actuaries and the Casualty Actuarial Society (CAS) contradicts previous findings. Using machine learning to identify patterns in Canadian and U.S. data from 2016 to 2019, the organization looked at the effect of the decriminalization of marijuana on vehicle accidents — and what they found about driving performance may surprise you.
The CAS researchers discovered that while being high on marijuana affects driving behavior, it may not be a bad thing. In fact, the study indicated some cannabis users were actually safer when they drove high, using slower speeds and longer following distances.
Looking at 10 regions in Canada, CAS concluded there were no statistically significant changes in the average cost per insurance claim or the frequency of claims since the legalization of marijuana in Canada in 2018. While results in the U.S. varied by state, CAS found that marijuana legalization and/or decriminalization failed to lead to a statistically significant change in fatality data. This accounted for weather and other factors that typically affect fatality data over weeks and years.5
Of course, just because some people who drive while impaired don’t suffer negative consequences doesn’t mean no one does. Still, it will be interesting to see how the data progresses as more U.S. states legalize and decriminalize recreational marijuana use. Will there be more evidence proving marijuana can make people better, not worse, at driving? Only time will tell.
Though it may or may not impair your driving, driving after ingesting marijuana is illegal across the U.S. and Canada. Make sure you only drive sober to keep yourself and others safe.
Marijuana and Driving: How to Keep Your Fleet’s Drivers Safe. Centers for Disease Control and Prevention. (2021, Nov 23).
Cannabis Act (S.C. 2018, c. 16). Government of Canada Justice Laws. (2022, Dec 12).
Cannabis Overview. National Conference of State Legislatures. (2022, May 31).
Cannabis (Marijuana) Research Report. National Institute on Drug Abuse. (2020, July).
Assessing the Impact of Marijuana Decriminalization on Vehicle Accident Experience. Canadian Institute of Actuaries. (2022, Dec).