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4/20 Is Linked to an Increase in Deadly Car Crashes

For drivers under 21, the weed holiday is as deadly as Super Bowl Sunday.

Denny Watkins

ROBYN BECK/AFP/Getty Images; Francine Orr/Los Angeles Times via Getty Images

The significance of April 20th as a stoner holiday has been attributed to police radio codes for marijuana possession (false) or the day Jimi Hendrix died (nope). But whatever the true origins, the date—along with the light-up time of 4:20 PM—is so popular that it’s spawned big public celebrations and civil disobedience rallies for legalization in Denver, San Francisco, London, and Washington DC, plus all the under-the-radar revelers in their homes or dorm rooms.

The only problem is, enough people across the US toke then try to drive that researchers found a 12 percent greater risk of dying in a car crash on April 20, according to a study published today in JAMA Internal Medicine.

Using 25 years’ worth of data from the US Department of Transportation’s Fatality Analysis Reporting System, researchers looked at the total number of fatal crashes that occurred between 4:20 PM and midnight on April 20 each year, compared to fatalities in the time period a week before and after that date.

Not only was the risk of a deadly accident 12 percent higher compared to control days for everyone on the road, but drivers under age 21 faced a 38 percent greater risk of a deadly accident. That higher risk is almost the same jump as the 41 percent spike in auto crash deaths on Super Bowl Sunday, a traditional heavy drinking day, according to prior research by study co-author Donald Redelmeier, a professor of medicine at the University of Toronto.

“The simplest interpretation of our findings is that some drivers are impaired by cannabis use and that these drivers contribute to fatal crashes,” says study author John Staples, a clinical professor at the University of British Columbia.


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The researchers started their data analysis with stats from 1992 because that was one year after a short blurb in cannabis magazine High Times explained the origins of 420. The write-up helped spread the tradition from Grateful Dead fans to broader pop culture. A 2017 study at the University of New Mexico reported that as many as 50 percent of college students surveyed get high on April 20.

Over the 25-year study period, the possible marijuana-linked crashes on April 20 add up to 142 additional deaths. Tragic for sure, but Staples points out that it’s just a fraction of the 37,000 auto fatalities in 2016 alone, of which roughly 10,000 deaths were alcohol-related, and another 3,500 were linked to distracted driving like texting and other bad habits. That said, weaving through traffic stoned is still no way to ensure you get home safe. “My message to the public is: Don't drive high,” Staples says.

Focusing on the popularity of marijuana use on 4/20 is one of the few ways to infer that marijuana contributes to fatal car crashes. Although alcohol intoxication levels in car crashes are dutifully reported throughout the DOT database, states and localities have widely varying standards for drug testing after a vehicle collision. “The largest group [of people involved in crashes] were those drivers for whom the police didn't test or didn't report on the involvement of drugs,” Staples says. “This makes drug-impaired driving difficult to evaluate using FARS data alone.”

The researchers were able to compare the relative crash risk between all 50 states, however, and the results are surprising. States with legal recreational marijuana like Washington and Colorado actually seem to have fewer crashes on April 20, while New York, Texas, and Georgia saw the biggest absolute increases in risk.

Relative increase in fatal car crashes on April 20 after 4:20 PM compared to one week prior and one week later. Brown corresponds to decreased risk, yellow is no change, and green shows an increased risk Courtesy of JAMA Internal Medicine

Keep in mind that looking at just a couple days of the year provides a only narrow window into how much weed people normally use. “Our study thus examines fluctuations in marijuana consumption on April 20th rather than base-rates of marijuana consumption,” Staples says. “It is possible that some states with high base-rates of cannabis consumption exhibit little increase in consumption on 4/20.” Marijuana legalization is also a fairly recent trend (both Colorado and Washington legalized recreational use in 2012), and this map shows 25 years’ worth of 4/20 auto crashes. The study did not report whether the crash rates seemed to be increasing or decreasing over those years in the US.

Ultimately, if you’re going to smoke and nibble on edibles on April 20, or any other day for that matter, make sure you have a sober ride home. Staples would also like to see 4/20 event organizers and the cities that host these celebrations encourage safe transportation plans for attendees like ride shares, taxis, designated drivers, and public transit.

“I think it's important that the regulatory and enforcement strategies around cannabis use and impaired driving prioritize public health,” Staples says. “This means there should be a focus on injury prevention, but it also means we should consider how our policy choices affect the health of marginalized groups such as minorities and people with mental health and addiction issues.”

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