Study: Adult-Use Marijuana Legalization Is Not Independently Associated with Increased Risk of Crash Victims Testing Positive for Cannabis

Hackensack NJ: The enactment of adult-use marijuana legalization laws is not independently associated with a rise in the percentage of motor vehicle crash victims testing positive for cannabis in hospitals, according to data published in the journal The American Surgeon.

Researchers affiliated with the Hackensack University Medical Center in New Jersey assessed trauma center patient data in states with and without adult-use legal marijuana laws over a 12-year period (2006 to 2018).

Investigators reported that the percentage of motor vehicle crash patients testing positive for cannabis increased over time in all of the states assessed (Arizona, California, Ohio, Oregon, New Jersey, and Texas). Overall, however, the greatest percentage change in cannabis-positive drivers occurred in Texas – where marijuana remains strictly prohibited. By contrast, California and Oregon – two states that have legalized the adult use and sale of marijuana – were among the states that experienced the lowest percentage changes over time. 

In a separate assessment, authors did not identify any significant changes in the percentage of motor vehicle accident patients testing positive for alcohol post-legalization. 

Authors determined, “There did not appear to be a relationship between the legalization of marijuana and the likelihood of finding THC in patients admitted after MVC (a motor vehicle crash).” They concluded, “There was no apparent increase in the incidence of driving under the influence of marijuana after legalization.”

Several prior studies have assessed whether the enactment of adult-use legalization is associated with any increased risk in the likelihood of motor vehicle accidents. The findings of those studies have yielded inconsistent results, with some studies identifying a minor uptick in crash rates several years following legalization, and others finding no such change.

Full text of the study, “Marijuana legalization and rates of crashing under the influence of tetrahydrocannabinol and alcohol,” appears in The American Surgeon. Additional information on cannabis, psychomotor performance, and accident risk is available from the NORML fact sheet, “Marijuana and Psychomotor Performance.