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Study: Medical Marijuana Access Not Associated With Greater Prevalence Of Cannabis-Positive Drivers

Thursday, 21 June 2018

Medical Marijuana and Driving

Atlanta, GA: The enactment of medical cannabis laws is not independently associated with a significant uptick in drug prevalence among fatally injured drivers, according to data published in the journal Accident Analysis and Prevention.

An investigator with Georgia State University assessed the relationship between the passage of medical marijuana access laws and the prevalence of fatally-injured drivers testing positive for the drug's presence over a 20-year period. The crash data made no determination with regard to whether the driver was either impaired at the time of the accident or if he/she was at fault.

The study concluded: "[M]edical marijuana laws in general have null effects on the prevalence of cannabis-positive driving. The key exception is for ... states that regulate the sale of cannabis though dispensaries, a policy framework that was shown to increase the probability of cannabis-positive driving by .011-.014, depending on the counterfactual policy. However, ... this is a relatively small effect, representing an additional 87-113 cannabis-positive drivers in 2014 who were involved in fatal vehicle accidents who might not otherwise have been."

Because THC's inactive metabolites may be present for weeks or even months following marijuana use, it is generally not possible to determine whether cannabis-positive subjects have recently ingested the substance or were under its influence at the time of a motor vehicle accident.

Prior studies have determined that neither the passage of medical marijuana laws or adult use cannabis laws is associated with an increase in overall traffic crashes or fatalities. According to the findings of a 2016 study published in The American Journal of Public Health, medical cannabis laws are associated with a reduction in traffic fatalities among drivers between 25 and 44 years of age. A separate study published that same year reported a decrease in the prevalence of opioid-positive drivers involved in fatal accidents following the enactment of medical marijuana legalization.

For more information, contact Paul Armentano, NORML Deputy Director, at: paul@norml.org. Full text of the study, "The effects of medical marijuana laws on cannabis-involved driving," appears in Accident Analysis and Prevention.