College students who consume energy drinks are more likely than their peers who don’t use them to abuse prescription drugs, a new study concludes. The more energy drinks a student consumes, the greater their risk.

The study included undergraduate and graduate college students, who completed a web-based survey about their pattern of energy drink and prescription stimulant use. They were asked about medications prescribed to them, as well as drugs they took without a prescription.

The more energy drinks students consumed, the likelier they were to illicitly use prescription stimulants. All students who had a valid prescription for stimulant medications said they mixed energy drinks with their stimulants. This is discouraged, because it can increase side effects, News-Medical.net reports.

The findings are published in Substance Abuse.

“This article includes a needed review of the neurological effects of energy drink ingredients. It also provides practitioners with important information about the dangerous interactions that can occur when energy drinks are mixed with prescription stimulants or other pharmaceutical drugs,” lead author Dr. Conrad Woolsey said in a news release. “Ginseng, for example, should not be mixed with anti-depressant medications or prescription stimulants because this can cause dangerously high levels of serotonin (i.e., serotonin syndrome), which is known for causing rapid irregular heartbeats and even seizures.”