Teens driving under influence of marijuana: Study finds

By Dr. Ananya Mandal, MDFeb 26 2012

According to a new survey too many teenagers are driving under the influence of marijuana believing it to be less dangerous than driving drunk.

The survey was conducted by Liberty Mutual Insurance and Students Against Destructive Decisions (SADD). They looked at 2,300 eleventh and twelfth graders and found more than one-third of teens who have driven after using marijuana say the drug doesn't distract them from driving. What's more, one in five teens admitted to driving high. In addition the survey found 13 percent of teens said they had got behind the wheel after drinking, while 19 percent did not consider drinking a major distraction.

“Marijuana affects memory, judgment, and perception and can lead to poor decisions when a teen under the influence of this or other drugs gets behind the wheel of a car,” Stephen Wallace, senior advisor for policy, research, and education at SADD, said in a written statement. “What keeps me up at night is that this data reflects a dangerous trend toward the acceptance of marijuana and other substances compared to our study of teens conducted just two years ago.” A 2009 survey from Liberty Mutual and SADD found 78 percent of teens considered smoking pot as “very” or “extremely” distracting to their driving.

According to the National Institute on Drug Abuse, using marijuana can cause distorted perceptions, impaired coordination, difficulty with thinking and problem solving, and problems with learning and memory.

About 90 percent of teen drivers in the latest survey said they wouldn't drive high if asked by their passengers. But only 72 percent of teen passengers said they'd say something to a driver who has used marijuana, compared with 87 percent who would speak up if the driver had consumed alcohol. Wallace told USA Today the survey's findings were “disturbing.” “We hear from young people who believe that marijuana actually makes them a safer driver, that they concentrate harder, drive slower,” he said.

The study highlights the need “to get the message out about the dangers of marijuana impairment,” says Tom Hedrick of The Partnership at Drugfree.org, an advocacy group that was not involved in the study. “It's a wake-up call for parents about the importance of having this conversation” with their teens.

“Teens are faced with potentially destructive decisions every day and don’t always make the best ones,” said Dave Melton, a driving safety expert with Liberty Mutual Insurance and managing director of global safety. “It’s our job as mentors, parents, role models or friends to effectively communicate with them to ensure they are armed with the right information and aware of the dangers of marijuana and other substances, especially while driving.”

Another new study of 50,000 drivers found motorists who smoked marijuana within three hours of getting behind the wheel were twice as likely to have a car accident, compared to sober motorists. A separate study in October found that 30 percent of fatally injured drivers tested positive for drugs other than alcohol, with marijuana topping the list. An earlier study by Hartford Hospital in Connecticut and the University of Iowa however, found that people who smoked pot 30 minutes before driving did not react much differently than they had before using marijuana.

NORML, the National Organization for the Reform of Marijuana Laws, wrote its own report on stoned driving in 2011, which found driving high might be riskier than driving sober, but less risky than driving drunk.