A survey of teenagers finds 22 percent of those taking controlled medications, such as painkillers or stimulants, misused the drugs in the past year. Misuse includes taking too much of the drug, intentionally getting high, or using the drugs to increase alcohol or other drugs’ effects.

Researchers at the University of Michigan conducted a web-based survey of almost 3,000 middle school and high school students. The survey covered sleeping pills, anti-anxiety medications, stimulants and opioid painkillers, Reuters reports.

The survey found 18 percent of the students said they used at least one of these drugs over the past year. Painkillers were the most commonly used drugs. Of those who used sleeping pills, 42 percent said they took more than the prescribed dose, and 17 percent used them to get high. Students who misused their prescriptions were more likely to smoke, binge drink and use illegal drugs, compared with those who followed their doctor’s orders.

One-third of teens who misused their prescriptions gave away or sold their medications—three times the rate of those who used the medications correctly.

The researchers published their findings in the Archives of Pediatrics & Adolescent Medicine.