Driving while stoned remains one of the biggest issues surrounding the burgeoning green rush as lawmakers grapple with how to address intoxicated motorists. While some opponents of cannabis, such as the The Automobile Club of Southern California (part of the national American Automobile Association, or AAA), came out against Proposition 64 for fear that an increase in pot use would lead to more traffic accidents, a new study suggests the opposite might be true.
Researchers at Columbia University’s Mailman School of Public Health found that states with medical marijuana laws saw an 11 percent decrease in traffic fatalities after legislation went into effect. The study, which was published online in the American Journal of Public Health, also concluded that these states have 26 percent fewer traffic fatalities compared to states without medical marijuana laws.
“We found evidence that states with the marijuana laws in place compared with those which did not, reported, on average, lower rates of drivers endorsing driving after having too many drinks,” says the study’s senior author Silvia Martins, MD, PhD, associate professor at the Mailman School.
“It is also possible that states with medical marijuana laws and lower traffic fatality rates may be related to lower levels of alcohol-impaired driving behavior in these states.”
The reduction in accidents impacted drivers between the ages of 15 and 44 and were most noticeable among those ages 25 and above. Conversely, this age group had the highest rate of drunken driving fatalities in 2004 and 2013, accounting for approximately 47 percent of road deaths involving a blood alcohol content 0.08 or higher.
California was one of two states where traffic fatalities actually fluctuated during the researchers’ study period. New Mexico is the other state where deaths initially went down several percentage points only to bounce back up within a few short years.
The study used data provided by the National Highway Traffic Safety Administration between the years of 1985 and 2014. Researchers accounted for median household income, unemployment rates, speeding and seatbelt laws and bans on texting while driving.
Traffic fatalities did not necessarily decrease among drivers over the age of 45, which is one of the fastest growing groups of marijuana users.
“This finding suggests that the mechanisms by which medical marijuana laws reduce traffic fatalities mostly operate in those younger adults, a group also frequently involved in alcohol-related traffic fatalities,” says Julian Santaella-Tenorio, a doctoral student at the Mailman School of Public Health.
As one of his final acts before Donald Trump takes office, President Barack Obama signed legislation last week directing the Department of Transportation to conduct studies on driving under the influence of weed. The federal government has also been ordered to increase public awareness campaigns addressing the dangers of drug-impaired driving, including the driving on heroin and prescription opioids. Within one year of implementation, DOT is to issue a report making recommendations on impairment standards for driving while stoned similar to the current 0.08 blood alcohol content limit that is used to legally define intoxication in the U.S.
“Marijuana users were about 25 percent more likely to be involved in a crash than drivers with no evidence of marijuana use,” says the National Highway Traffic Safety Administration on its website. “Other factors – such as age and gender – appear to account for the increased crash risk among marijuana users.”
In other words, “marijuana users are more likely to be involved in accidents, but that the increased risk may be due in part because marijuana users are more likely to be in groups at higher risk of crashes,” the NHTSA press release explained. “In particular, marijuana users are more likely to be young men – a group already at high risk.”
The University of San Diego's Cannabis Research Center is currently studying how THC levels impact driving. The center's findings will influence how California officials legislate stoned driving as recreational pot gets underway next year.