An article in the Canadian Medical Association Journal says doctors should consider refusing requests by healthy patients for cognitive-enhancement drugs like those used to treat attention deficit disorder.

Prescription stimulants such as Ritalin and Dexedrine are often used by people for "cognitive enhancement" to increase focus, concentration and memory.

Co-author Cynthia Forlini of McGill University in Montreal says there is little evidence that the medications benefit healthy people and their side-effects may cause harm.

She says it's not clear how many healthy people use these drugs to try to boost brain power, but some studies suggest up to 11 per cent of university students take them.

Forlini says some people get the drugs from peers or family members being treated for ADD or through black market channels.

The authors suggest that prescribing cognitive enhancers to healthy people is not a good use of resources under Canada's publicly funded health-care system.