No Increase in DUI Among Young Adults After Pot Legalization in Washington

Trends may reflect some success in highway safety, but additional research is needed.

Newly published research indicates that recreational cannabis legalization in Washington did not result in a spike in impaired driving among younger demographics.

The research, published last month in the journal Prevention Science, was based on data collected in the five years following legalization.

“Motor vehicle crashes are a leading cause of death for young adults (YA) in the USA, and driving under the influence of alcohol (DUIA), cannabis (DUIC), and simultaneous use of both substances (DUIAC) are prominent risk factors,” the authors explained in the study’s abstract. 

“Trends in YA impaired driving behaviors after opening of cannabis retail stores have been understudied. We examined YA trends in DUIA, DUIC, and DUIAC from immediately prior through 5 years following the opening of cannabis retail outlets in Washington State (2014–2019).”

They noted that differences “in trends were assessed across age, sex, and urbanicity,” and that “weighted logistic regressions assessed yearly change in prevalence of DUIA, DUIC, and DUIAC from 2014 to 2019, using annual statewide data from the Washington Young Adult Health Survey (n = 12,963; ages 18–25).” 

“Moderation of trends by age, sex, and urbanicity was assessed. Prevalence of DUIA decreased overall (AOR = 0.93, 95% CI 0.90, 0.97) and among drinkers (AOR = 0.95, 95% CI 0.91, 0.99) but remained at concerning levels in 2019 (10% overall; 16% among drinkers),” they said.

Ultimately, the researchers found that driving under the influence of cannabis “did not change significantly…but decreased among those who used cannabis.” 

Driving under the influence of alcohol and cannabis simultaneously “decreased but not significantly,” according to the researchers, who said that the “prevalence of [young adult] DUI remained concerning.”

As NORML pointed out, the findings have echoes of a 2022 study that found that the “risk of self-reported [driving under the influence of cannabis] was lower in recreational and medical cannabis states compared to states without legal cannabis.”

The authors of that study, published in Preventive Medicine Reports, said they were motivated to research the matter because the “relationship between cannabis legalization and traffic safety remains unclear.”

“Physiological measures of cannabis impairment remain imperfect. This analysis used self-report data to examine the relationship between cannabis legalization and driving under the influence of cannabis (DUIC),” they said.

Those researchers said they used “a cross-sectional national sample (2016–2017) of 1,249 past–30-day cannabis users,” and then “regressed self-reported DUIC (driving within three hours of ‘getting high’) on cannabis legalization (recreational and medical (recreational), medical only (medical), or no legal cannabis), adjusting for demographics, days of use (past 30 days), days of use, legal status, calibration weights, and geographic clustering.”

“The risk of DUIC in recreational (risk ratio [RR] = 0.41, 95% confidence interval (CI):0.23–0.72) and medical (RR = 0.39, 95% CI:0.20–0.79) states was lower than in states without legal cannabis, with one exception. Among frequent cannabis users (≥20 days per month), there was a significantly lower risk of DUIC for those living in recreational states (RR = 0.70, 95% CI: 0.49–0.99), but not for those living in medical states (RR = 0.87, 95% CI: 0.60–1.24), compared to users living in states without legal cannabis,” the authors explained.

They said that while “all states should educate its citizens about the potential dangers of using cannabis and driving, this analysis suggests that states without legal cannabis are particularly in need of DUIC prevention efforts.” 

“States should consider mass media campaigns as a method of reaching all cannabis users, including more frequent users, with information about the dangers of DUIC. Medical states may consider targeting frequent users by disseminating information about DUIC through medical dispensaries. Further research is warranted, particularly given the constantly evolving nature of cannabis legalization and the noted limitations of this analysis,” the authors said, as quoted by NORML.

The findings are encouraging because, generally, toking and driving should be avoided.

A study released earlier this year using cannabis could be particularly detrimental to older drivers.

“Epidemiological studies have established that cannabis increases the risk of a motor vehicle collision,” the study’s authors wrote. “Laboratory studies have demonstrated that this impairment results in increased weaving, slowed reaction time, and compensatory changes in speed and following distance.”

“Older adults may be particularly affected by cannabis, given age-related changes in cognition, metabolic changes that may prolong or enhance the effects of cannabis, and the concomitant use of medications,” they added. “Conversely, older users of cannabis may have been using cannabis for many years and cannabis may have a diminished impact in this population due to development of tolerance.”

The study was conducted by researchers in Canada, where marijuana is legal for adults.

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