MONDAY, Aug. 1 (HealthDay News) -- More than one in five teens who have been prescribed a controlled medication such as Oxycontin for pain or Ritalin to treat attention deficit hyperactivity disorder are misusing the drugs, a new study has found.

And these kids are more likely than others to abuse other substances and to start giving or selling drugs to their peers, the researchers said.

Still, it's important to remember that most kids do take their medications as prescribed, the team added.

"The fact that we can now say the majority of secondary school kids who are prescribed opioids and other controlled medications [do not abuse then] is important because the field doesn't want to go back to having so much fear associated with these medications that we then underprescribe them," stressed Sean Esteban McCabe, lead author of a study on teens and controlled medications appearing in the August issue of Archives of Pediatrics. "Some of these students are in school because they use their medications appropriately. If they didn't have access, they might not be in school."

McCabe is associate professor at the Institute for Research on Women and Gender and at the Substance Abuse Research Center of the University of Michigan in Ann Arbor.

Nevertheless, the results are also a good argument for screening which kids should be prescribed these medications, or which should be monitored more stringently, said another expert.

"We need to have an understanding that misuse or diversion can occur, so we have to be able to screen people effectively for risk factors for substance abuse," said Dr. Howard Liu, a child and adolescent psychiatrist at the University of Nebraska Medical Center in Omaha. "Parents also need to be able to control medications and that means securing or locking up controlled medications and also getting rid of them when they're no longer needed."

As the number of controlled medications prescribed to youngsters increases, so does the risk of their abuse and misuse.

The Michigan team set out to gauge rates of misuse for four types of controlled medications: painkillers, stimulants, sleeping meds and anti-anxiety drugs.

About 2,600 middle- and high-school students from two school districts in southeastern Michigan responded to a Web-based survey. The average age was about 15.

Almost one in five (18 percent) of the respondents said they had used at least one prescribed controlled medication during the past year.

Of those, 22 percent said they had misused the medication, usually by taking too much.

These kids were almost eight times more likely to test positive for drugs compared with those who used their medication appropriately, and they were more likely to start selling or giving the drug to others, the study authors said.

Kids who used pain, sleeping and anti-anxiety medications more frequently were more likely to abuse them, though the same wasn't true of stimulants.

The misuse of prescription medications is a growing concern. Among Americans in general, abuse of prescription painkillers has surged alarmingly in recent years. Treatment admission rates for abuse of opiates other than heroin -- including prescription painkillers such as Oxycontin -- rose by 345 percent from 1998-2008, according to federal data.

A second study, this one appearing in Archives of General Psychiatry, found that people who "self-medicate" their anxiety symptoms with drugs or alcohol are more likely to become substance abusers.

U.S. adults who self-medicated were also more likely to develop social phobia, according to a team from the University of Manitoba, Canada.

More information

For more information on controlled substance abuse, visit the U.S. National Institute on Drug Abuse.