OREANDA-NEWS  One-third of young adults aged 19 and 20 report riding in a motor vehicle with an impaired driver at the wheel at least once in the past year, according to a new study co-authored by Yale researcher Federico Vaca, M.D., M.P.H, and his colleagues at the National Institutes of Health, and led by Colorado State University investigators. Driver impairment was more likely to be caused by marijuana use than alcohol, the researchers said.

The research team used data from the NEXT Generation Health Study, a nationally representative survey of U.S. adolescents and young adults focusing on health and behavior. They analyzed responses from young adults one to two years out of high school who were asked about a variety of health topics, including risky behavior and substance use.

One-third of the group surveyed said they had taken a ride with an impaired driver. More specifically, in response to a question about riding in a vehicle driven by someone who had had an alcoholic drink or drug, 23% of the young adults said they had done so with a driver impaired by marijuana. One in five said they had ridden along with an alcohol-impaired driver.

The study was also the first to ask about the impaired driver’s age and relationship to the young adult. They were more likely to be riding with an impaired peer than with an impaired adult — 21% versus 2.4% for marijuana, 17% versus 4% for alcohol, the researchers said.

The fact that so many young adults have been passengers in a car with an impaired driver is concerning, said the researchers, especially since taking the risk once not only increases the chance that the risky behavior will be repeated but it also predicts that the passengers, too, will engage in impaired driving in the future. The study findings underscore the need to raise awareness and combat the perception that impaired driving is acceptable, said Vaca, who is a professor in the Department of Emergency Medicine and in the Child Study Center. He directs the DrivSim Lab, a research initiative that seeks to reduce car crashes.

Motor vehicle crashes are the leading cause of death and injury among teens and young adults, according to the Centers for Disease Control and Prevention.