Up to 20% of adults may be using prescription drugs such as Ritalin to increase alertness and brain power, according to a survey of 1,400 people, BBC New reported.

The Nature journal poll found that 20% of respondents said they'd taken Ritalin, Provigil (modafinil) or beta-blockers for non-medical reasons such as boosting focus, concentration or memory. Of those, 62% had taken Ritalin and 44% Provigil, which is normally prescribed to treat daytime sleepiness in people suffering from the sleep disorder narcolepsy, the news service said.

In most cases, users of the drugs got the drugs through prescriptions or bought them online.

Professor Barbara Sahakian, of Addenbrooke's Hospital in Cambridge, England, said there's evidence that the use of drugs for cognitive enhancement is becoming more widespread and safety trials are urgently needed, BBC News reported.

"We do not really have long-term efficacy and safety data in healthy people. These are studies that really need to be done," Sahakian said. "The use of cognitive enhancing drugs is spreading to younger and younger people. That's a concern."