Some Winnipeg university students preparing for exams are using a drug typically prescribed for attention deficit hyperactivity disorder (ADHD) to help them study, even though they don't have prescriptions.

One University of Manitoba student told CBC News he recently purchased Adderall XR from a friend so he can focus on schoolwork for longer periods of time.

CBC News has agreed to conceal the identity of the student, who said he purchased the pills from a friend who knows someone with a valid prescription.

"I have five of them on me here," the student said.

"I feel it's helping me concentrate and focus on the schoolwork," he added. "[It's] much easier than without it."

It's not known how many post-secondary students are using Adderall or similar ADHD drugs, like Ritalin, to help them study.

A 2011 editorial in the Canadian Medical Association Journal called on campus administrators to educate students on the dangers of illicit stimulant use.

Students may abuse prescription drugs like Ritalin for a perceived boost in academic performance through enhanced attention and alertness, but the editorial said evidence suggests no boost in cognition among those using the stimulants.

The research does suggest potential health risks, including death, life-threatening hypertension and heart rhythm disturbances, serious overdoses, dependence and depression, according to the editorial.

Officials with the University of Manitoba told CBC News that there is no evidence "study drugs" can help students achieve better grades, so their use is not considered to be cheating.