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Affiliation
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Division of General Internal Medicine, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada. |
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Abstract
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On April 20 each year, thousands of Americans celebrate the intoxicating properties of marijuana on a popular counterculture holiday known as “4/20.” Legal marijuana sales surge in anticipation of the “High Holiday,” and college students report increased cannabis consumption on 4/20 itself.1,2 In many cities, activists and enthusiasts gather at public celebrations that feature synchronized mass consumption of cannabis at 4:20 pm.3
Driving simulation studies indicate that higher blood Δ9-tetrahydrocannabinol concentrations decrease reaction times and increase variability in speed and lane position, while some epidemiologic studies suggest that acute cannabis intoxication increases crash risk.4 Despite this evidence, driving after cannabis consumption is surprisingly common.5 We hypothesized that the April 20 cannabis celebration might be associated with a population-level increase in the risk of fatal traffic crash involvement.
Methods
This study used publicly available statistical data with a waiver of approval from the University of British Columbia research ethics board. We obtained fatal motor vehicle crash data from the United States National Highway Traffic Safety Administration’s Fatality Analysis Reporting System (FARS). FARS includes data on all crashes involving a motor vehicle traveling on public roadways in which at least 1 participant died within 30 days of the event. The study interval began the first full year after popularization of 4/20 in High Times magazine and extended to include the most recent year with data available, thereby reflecting 25 consecutive years (January 1992 to December 2016).
The primary analysis compared the number of drivers involved in fatal traffic crashes between 4:20 pm and 11:59 pm on April 20 each year to the number in fatal traffic crashes during the same time intervals on control days 1 week earlier and 1 week later (ie, April 13 and April 27). This design controlled for weekday, season, and year while minimizing bias from changes in vehicle design, travel distances, medical care and other confounders. We tested for differences between case and control dates using exact binomial tests and performed prespecified stratified analyses to examine individual factors and geographic variation.
Results
The 25-year study interval identified 1.3 million drivers involved in 882 483 crashes causing 978 328 fatalities. In total, 1369 drivers were involved in fatal crashes after 4:20 pm on April 20 whereas 2453 drivers were in fatal crashes on control days during the same time intervals (corresponding to 7.1 and 6.4 drivers in fatal crashes per hour, respectively). The risk of a fatal crash was significantly higher on April 20 (relative risk, 1.12; 95% CI, 1.05-1.19; P = .001)...
Keyword: Cannabis impaired driving
Language: en |