A prescription for an opioid drug such as Percocet or Vicodin can offer pain relief, but it also comes with the potential for abuse and addiction. In the past 20 years the number of overdose deaths from these drugs has more than tripled. In examining whether a legitimate prescription for opioid drugs increases the likelihood of later misuse for teens, a recent study uncovered a surprising trend: it's the drug-naive teens who are most at risk.

Sociologist Richard Miech of the University of Michigan and his team analyzed data about high school seniors from the ongoing Monitoring the Future project, an annual survey that tracks the alcohol and drug use of representative samples of eighth, 10th and 12th graders in the U.S. The new study, published in November 2015 in Pediatrics, included more than 6,000 12th graders who had been randomly selected for follow-up questions about opioid misuse when they were between the ages of 19 and 23.

Overall, young adults who had taken opioids with a prescription by 12th grade were 33 percent more likely to misuse the drugs after high school than those who had not been prescribed opioids. But the researchers also broke down the data based on the teens' history of, and attitudes regarding, illicit drug use. Teens with a lot of drug experience were likely to misuse an opioid after high school whether or not they had had a prescription by 12th grade. Instead the risk stemming from a legitimate prescription was concentrated among teens who were previously thought to have a low likelihood of misusing opioids.

These teens had very little experience taking illicit drugs, and they disapproved of marijuana use. Yet if the drug-naive kids had a prescription for opioids by 12th grade, they were three times more likely to misuse them by age 23 than similar teens who never had a prescription.

“These results suggest that we shouldn't overlook kids who are not using drugs when they are younger,” Miech says. Even though the vast majority misused opioids infrequently—no more than five times in a year—being drug-naive “makes their misuse potentially more dangerous,” Miech says. “They may not realize that taking a couple of opioids after a night of drinking could have lethal consequences.” But on the plus side, “these kids already go into the doctor's office with attitudes against drugs and are likely to listen,” he adds, so doctors and parents should make the effort to inform them of the risks of taking opioids outside of a doctor's care.