This is What Happens When You Drive on Pot and Alcohol

Teens who mix alcohol and marijuana are terrible drivers, new research suggests.

Researchers took a look at yearly surveys of over 72,000 U.S. high school seniors from 1976 to 2011, and assessed their simultaneous use of pot and alcohol. They found that teens who reported using both at the same time were 50 to 90% more likely to admit to unsafe driving than teens who did not smoke pot or drink. About 40% of teens who used both at the same had received a traffic ticket or warning over the last year, and about 30% had been in an accident.

Driving under the influence of alcohol and drugs is known to be dangerous, but less is known about combining the two and going behind the wheel. Though there are several theories for why these teens are at a greater risk, the answer is still unclear. According to the researchers, the combination may impair both teens’ driving and judgement, and it’s also possible that teens that use both together are also bigger risk takers in general.

On the bright side, drinking and marijuana use has declined over time. A third of high school seniors said in 2011 that they had not used either in the past year. Only 12% could say the same in 1979.

The study is published in the Journal of Studies on Alcohol and Drugs.