A new study finds college students who use prescription drugs for non-medical purposes are at increased risk of depression and thoughts of suicide.

The researchers analyzed the answers of 26,600 college students who participated in a national research survey by the American College Health Association. They were asked about their non-medical prescription drug use, including painkillers, antidepressants, sedatives and stimulants, as well as their mental health symptoms in the past year.

About 13 percent of students reported non-medical prescription drug use, Science Daily reports. Those who reported feeling sad, hopeless, depressed or considered suicide were significantly more likely to report non-medical use of any prescription drug. The link between these feelings and prescription drug abuse was more pronounced in females, the researchers report in Addictive Behaviors. The researchers conclude that students may be inappropriately self-medicating psychological distress with prescription medications.

“Because prescription drugs are tested by the U.S. Food and Drug Administration and prescribed by a doctor, most people perceive them as ‘safe’ and don’t see the harm in sharing with friends or family if they have a few extra pills left over,” researcher Amanda Divin of Western Illinois University said in a news release. “Unfortunately, all drugs potentially have dangerous side effects. As our study demonstrates, use of prescription drugs — particularly painkillers like Vicodin and OxyContin — is related to depressive symptoms and suicidal thoughts and behaviors in college students. This is why use of such drugs need to be monitored by a doctor and why mental health outreach on college campuses is particularly important.”