Updated

More than one in five teens who get strong painkillers, stimulants or other controlled medications from their doctor take too much of the substances, according to a new survey of Michigan students.

Usually kids take too much of the drugs, risking dangerous side effects, but as many as 10 percent use them intentionally to get high, researchers said Monday.

"There has been an increase in the prescribing of controlled substances in the last 15 years, but there has also been an increase in the non-medical use of these substances," said Sean Esteban McCabe from the University of Michigan in Ann Arbor, who worked on the survey.

He and his colleagues used a Web-based survey to test teenagers' use of four groups of controlled medications they had received from their doctors, including sleeping pills like Ambien, antianxiety medications like Xanax, stimulants like Ritalin and opioid painkillers like OxyContin.

The team's findings are published in the Archives of Pediatrics & Adolescent Medicine.

Overall, 18 percent of nearly 2,600 students from Detroit-area middle and high schools said they had used one such drug to treat a medical condition over the past year.

Painkillers were the most common drugs, followed by stimulants and sleeping pills. Overuse was particularly common with sleeping pills, which 42 percent of users took in quantities higher than the prescribed dose and 17 percent used to get high.

Teens who strayed from the doctors' prescriptions were more likely to smoke, binge drink and use illegal drugs than those who followed medical instructions.

They also sold or gave away their medicine more often. For instance, a third of them said they'd given or loaned their drugs to others at some point — three times as many as among youngsters who didn't misuse their medications.

"Kids are most likely to get medications that are not prescribed to them from their peers," McCabe told Reuters Health, adding that the majority of kids get the controlled substances for free.

While most youngsters use their medicine appropriately, according to the new study, McCabe said the findings suggested that stricter monitoring might be called for.

"Parents play an important role. The big take-home here is that it is important to step up monitoring of adolescents and to prescribe the appropriate amount of medications," he said. "For those kids who are misusing these medications, and have higher risk of substance abuse, it is not that they shouldn't get the medications, but they need to be monitored more closely."