Study: Marijuana Legalization Laws Not Are Associated with Lax Attitudes Toward Drugged Driving

Adults in states where the use of cannabis is legal are less likely than those in non-legal states to report having driven under the influence of cannabis, according to data published in the journal Preventive Medicine Reports.

Investigators affiliated with the research institute RTI International assessed drugged driving attitudes and behaviors in a nationwide cohort of 1,249 current marijuana consumers.

The study’s authors reported: “Current cannabis users in recreational and medical only cannabis states were significantly less likely to report driving within three hours of getting high in the past 30 days, compared to current users living in states without legal cannabis. The one exception was frequent cannabis users who lived in medical cannabis states. Their risk of DUIC [driving under the influence of cannabis] did not differ significantly from frequent users living in states without legal cannabis.”

Commenting on the study’s findings, NORML’s Deputy Director Paul Armentano said: “These findings ought to reassure those who feared that legalization might inadvertently be associated with relaxed attitudes toward driving under the influence. These conclusions show that this has not been the case and that, in fact, consumers residing in legal marijuana states are less likely to engage in this behavior than are those residing in states where cannabis possession remains criminalized.”

Authors theorized that consumers in legal marijuana states may have greater exposure to messaging highlighting the risks and legal ramifications associated with drugged driving.

“Although 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,” they concluded. “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 study’s results are consistent with the findings of a 2021 paper which similarly determined that incidences of self-reported drugged driving behavior do not become more prevalent post-legalization. Rather, authors reported, “[M]arijuana users in states that legalized RM [recreational marijuana] self-reported driving after marijuana use less than their counterparts (who resided in states where adult-use cannabis remained illegal). They were also less likely to find such behavior [driving after ingesting cannabis] acceptable.”

Numerous on-road and driving simulator studies have reported that the acute effects of THC inhalation are associated with certain changes in driving behavior, such as an increased likelihood of weaving and a decrease a drivers’ average speed. These and other changes are typically less pronounced in subjects who are more habitual cannabis consumers, but they may be exacerbated when alcohol and marijuana are ingested in combination with one another.

State-level data has failed to show any uptick in motor vehicle accidents attributable to the enactment of medical cannabis laws, while data assessing the potential impact of adult-use legalization has shown less consistent results.

Full text of the study, “Cannabis legalization and driving under the influence of cannabis in a national U.S. sample,” appears in Preventive Medicine Reports. Additional information regarding marijuana use and traffic safety is available from the NORML fact-sheet, “Marijuana and Psychomotor Performance.”