Doctors Can't Figure Out What's Causing Car Crashes on 4/20

They're hesitant to draw any hasty conclusions.

Flickr / Cannabis Culture

We all know driving drunk is a risky proposition, but what about stoned driving? While the effects of marijuana include slowed reaction time and impaired coordination, scientists have still been hesitant to factor it in as a culprit in car crashes because it’s not clear how to measure it in impaired drivers. A new article in JAMA Internal Medicine, however, presents evidence that’s hard to argue with.

In the research letter published Monday, doctors examined data for 25 years and found that the 4/20 holiday was associated with a 12 percent increase in fatal traffic accidents from 4:20 P.M. to midnight when compared to the week before and after.

The study’s authors, University of British Columbia clinical assistant professor of medicine Dr. John Staples and University of Toronto professor of medicine Dr. Donald Redelmeier, report that the increased risk is particularly pronounced for drivers 20 years old and younger.

“Although the vast majority of Americans do not celebrate 4/20, the observed association was comparable in magnitude to the increase in traffic risks observed on Superbowl Sunday,” the study’s authors report.

Doctors found that 4/20 can be just as deadly as Superbowl Sunday.


This research comes at a time when more and more U.S. states are legalizing marijuana in one way or another, with debates raging over whether law enforcement officers can police stoned driving. Multiple companies are trying to rush cannabis breathalyzers to market, but the unique pharmaceutical properties of marijuana make it much more difficult than alcohol breathalyzers.

The National Highway Traffic Safety Administration reports that, according to 2016 statistics, an average of nearly 29 people die from alcohol-related crashes each day. The numbers for marijuana-related crashes are a little less clear, though. The National Institute on Drug Abuse reports conflicting results among various studies: Some studies show that marijuana concentration in the bloodstream is correlated with car crashes, but that can be misleading since THC can stay in the bloodstream for a month after smoking. Additionally, other studies show no correlation between marijuana consumption and car crashes once researchers control for other factors.

A major weakness of this newest study is that it does not control for drug or alcohol consumption besides marijuana, so it’s hard to draw a definite conclusion from this paper. As always, more research will be necessary to draw any definite conclusions about the public health implications of the 4/20 holiday.

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