The legalization of marijuana has recently gained more momentum in the U.S., since states like Colorado and Washington allow the sale and possession of the drug for both medicinal and recreational use. However, there may be a dark side to the benefits of pot when it comes to getting behind the wheel. According to a recent study published in the American Journal of Epidemiology, fatal pot-related car crashes have tripled in the U.S. over the last 10 years, posing the question: Is driving under the influence of marijuana dangerous?

In a culture that has continually stressed the effects of drunk driving, most people are aware of the potentially fatal danger of mixing alcohol and driving, but awareness of drugged driving is not as widespread. Drugged driving, such as driving under the influence of pot, poses an equal danger to drunk driving on the nation’s highways. The National Institute on Drug Abuse says the use of any psychoactive drug makes driving a car highly unsafe, putting not only the driver in danger, but also passengers and other drivers on the road. Although the effects of specific drugs differ on how they act in the brain, they all impair abilities necessary for safely operating a vehicle. A driver’s motor skills, balance and coordination, perception, attention, reaction time, and judgment are all altered by the use of these mind-altering drugs.

Young drivers are found to be particularly at risk for drugged driving based on data on youth behaviors. An estimated 10.3 million people aged 12 or older, reported driving under the influence of illegal drugs, according to the 2012 National Survey on Drug Use and Health. Now a team of researchers at Columbia University's Mailman School of Public Health, sought to assess just how prevalent marijuana use was in a series of fatal car crashes over the course of 10 years.

Data drawn from the National Highway Traffic Safety Administration's Fatality Analysis Reporting System was obtained to assess the trend of the prevalence of non-alcohol drugs detected in fatally injured drivers in the U.S. The statistics included more than 23,500 drivers from six different states, who were dead within one hour of a car accident between 1999 and 2010. California, Hawaii, Illinois, New Hampshire, Rhode Island, and West Virginia, were among the six states examined in the study. These states routinely perform toxicological testing on drivers involved in fatal car crashes.

The findings revealed alcohol contributed to about the same percentage of traffic fatalities throughout the decade, roughly at 40 percent. However, drugs were seen to play an increasingly prevalent role in fatal car crashes, accounting for more than 28 percent of deaths in 2010, compared to 16 percent in 1999. The biggest drug culprit was found to be marijuana, jumping from four percent in 1999 to 12 percent in 2010, or triple the amount.

"Currently, one of nine drivers involved in fatal crashes would test positive for marijuana," said Dr. Guohua Li, co-author of the study and director of the Center for Injury Epidemiology and Prevention at Columbia told HealthDay. "If this trend continues, in five or six years non-alcohol drugs will overtake alcohol to become the most common substance involved in deaths related to impaired driving." In addition, the combination of alcohol and marijuana use will dramatically increase a driver’s risk of death 24 times that of a sober person.

These statistics could be sobering for teens who believe drugged driving is safer than drunk driving. Marijuana affects a person’s concentration, perception, and reaction time up to 24 hours after it’s smoked. This is much longer than the duration in which alcohol can affect a person’s behavior.

In a study published in the New England Journal of Medicine, researchers found drugs and driving are a bigger problem than previously thought. The report unveiled 45 percent of drivers who were stopped by police for reckless driving had marijuana in their systems, while 25 percent had cocaine. None of these drivers had alcohol in their systems.

These studies highlight the need for an accurate test to check a driver’s marijuana intoxication during a traffic stop. Currently, a test using a driver’s salvia is available to check for cannabis levels, but it is not viewed as precise as the Breathalyzer, and has not been widely used by the police, according to Li. The urgency for an efficient testing method or technique lies in the fact that marijuana users who get behind the wheel may be pulled over for their erratic driving, but are usually let go. These drivers pass the Breathalyzer tests since alcohol is not in their system, and current marijuana tests are not as reliable or accurate.

While there is an established evidence that alcohol increases accident risk, evidence of marijuana’s effects on driving are slowly surfacing. Driving under the influence of marijuana, alcohol, or both impairs a driver’s judgment, putting in danger themselves and all those on the road. Those who are operating a motor vehicle are advised to not drink or smoke pot and drive, to save lives.


Brady JE and Li G. Trends in Alcohol and Other Drugs Detected in Fatally Injured Drivers in the United States, 1999–2010. Journal of Epidemiology. 2014.

Brokoff D, Cook CS, Mann CS, and Williams C. Testing Reckless Drivers for Cocaine and Marijuana. New England Journal of Medicine. 1994.