College students’ anxiety about tests can cause poor sleep. That, in turn, can result in poor test performance, and even more anxiety. It’s a vicious cycle, and learning how sleep, anxiety and exam performance are related is the first step toward addressing it.

Researchers at the University of Kansas wanted to know how much those factors affected each other. They focused on a typically stress-inducing class: statistics. Students completed sleep diaries and other tests in the days before an exam. Even after accounting for factors such as students’ past performance, they found test anxiety and poor sleep were consistent predictors of who would pass an exam. Typically, extreme anxiety accounted for a 5% difference in test scores.

They also found that measures used to combat test anxiety can sometimes exacerbate sleep problems. Using caffeine to study longer or to stay alert during the day actually enhanced sleep problems.

But there are some strategies for combating test anxiety and its effects on students’ lives. For the most common anxiety-inducing classes — typically math and statistics — instructors should encourage students to spend a few minutes before an exam writing about what makes them edgy. Eliminating time limits for exams would also help anxious students. That’s because time limits don’t measure a student’s full ability, only their ability to do certain things quickly.

The lessons learned from the study go beyond the classroom. If an upcoming event or activity is testing your emotional limits, make sure you get plenty of rest. It will help clear your mind so you can ace whatever test you’re facing.