NEW YORK — Teens who’ve been in cars with impaired drivers may be more likely themselves to get behind the wheel drunk or drugged, a recent study suggests. And the more times they’re driven around by an impaired driver, the more risky their own driving habits become.

While other studies have found ties between riding with impaired drivers and teen impaired driving risk, the new study surveyed about 2,500 U.S. students each year between 10th and 12th grades to examine rates over time — not at just one point.

“We were interested in both driving while intoxicated and riding with an intoxicated driver, because it’s the combined of the two behaviors that reflects the true risk,” Bruce Simons-Morton, one of the researchers, told Reuters Health.

“When you do that, you see a relatively high proportion — about 30 percent in our study — reported either driving while intoxicated or riding with an intoxicated driver within the last three years,” he said.

Overall, between 12 percent and 14 percent of students each year reported impaired driving in the past month and 23 percent to 38 percent reported riding in cars with drunk or drugged drivers within the past year, the researchers wrote in Pediatrics.

Students were more likely to drive impaired if they had been in cars with impaired drivers after adjusting the numbers for the students’ genders and drinking and drug habits, family income, and parental education and supervision.

Specifically, kids who reported riding with drunk or drugged drivers during one of the surveys were 10 times more likely to drive drunk or drugged than a kid who never reported riding in cars with impaired drivers.

That risk grew to 34 times greater when they reported riding in cars with impaired drivers on two surveys and 127 times greater if they reported riding in cars with drunk or drugged drivers on all three surveys.

“The magnitude of the association kind of gets one’s attention,” said Simons-Morton.

Simons-Morton is from the Health Behavior Branch of the National Institute of Child Health and Human Development, which is part of the National Institutes of Health, in Bethesda, Maryland.

He and his colleagues note that they can’t distinguish exposure to only drunk or drugged driving in their results, however. They also can’t say whether the impaired drivers the students reported riding with were other young people or adults.

But they say that early exposure to impaired driving may come across as “normal” behavior to teens, who may be particularly impressionable.

“When you ride with an intoxicated driver, it sort of normalizes the idea of drinking and driving,” Simons-Morton said. “Also, you’re around peopling who drink and drive.”

He added that current policies to discourage drunk and drugged driving among teens are acceptable, but parents and peers need to be persistent.

“The primary issue is not driving or riding with an intoxicated driver,” Simons-Morton said. “You want to plant the important message in your teens’ heads.”

SOURCE: Pediatrics, online March 17, 2014.