In the middle of the exam season, the offer of a drug that could improve results might excite students but would be likely to terrify their parents. Now, a distinguished professor of bioethics says it is time to embrace the possibilities of "brain boosters" – chemical cognitive enhancement. The provocative suggestion comes from John Harris, director of the Institute for Science, Ethics and Innovation at the University of Manchester, and editor-in-chief of the Journal of Medical Ethics.

Ritalin is a stimulant drug, best known as a treatment for hyperactive children. But it has also found a ready black market among students, especially in the US, who are desperate to succeed and are turning to it in preference to the traditional stimulants of coffee and cigarettes. Users say it helps them to focus and concentrate, and this has been confirmed in research studies on adults.

David Green, a student at the University of Harvard, told The Washington Post: "In all honesty, I haven't written a paper without Ritalin since my junior year in high school."

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Matt, a business finance student at the University of Florida, claimed a similar drug, Adderall, had helped him improve his grades. "It's a miracle drug," he told The Boston Globe. "It is unbelievable how my concentration boosts when I use it."

Some experts have condemned the trend and accused students of gaining an "unfair advantage" by doping, without explaining why it is any more unfair than hiring a private tutor or paying for exam coaching.

Professor Harris says that the arguments against the drugs "have not been persuasive" and that society ought to want enhancement.

"It is not rational to be against human enhancement," he writes. "Humans are creatures that result from an enhancement process called evolution and moreover are inveterate self improvers in every conceivable way."

Although no drug can be guaranteed safe and free of all side-effects, Ritalin has been judged safe enough for children with attention deficit hyperactivity disorder (ADHD), and has been widely used to treat them over many years, he says.

The drug is a stimulant which was introduced in 1956 and appears to influence the way the brain filters and responds to stimuli. It increases energy as well as confidence and has been compared to cocaine. Possible side-effects are typical of stimulants and include insomnia, loss of appetite, dizziness and depression on withdrawal.

Other drugs investigated for their mind-enhancing properties include donepezil, a treatment for dementia and modafinil, used in narcolepsy, the condition in which sufferers repeatedly fall asleep.

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Both drugs are thought to boost highly skilled performance, where concentration and alertness are prerequisites. One study found commercial pilots who took donepezil for one month performed better than pilots on a placebo when dealing with emergencies on a flight simulator. A study of modafinil found that it boosted the performance of helicopter pilots flying on simulators who had been deprived of sleep.

Writing in the online British Medical Journal, Professor Harris says the use of cognitive enhancing drugs should be seen as a natural extension of the process of education. Drug regulatory agencies should assess the benefits and risks in the same way as they would for any other medical intervention.

"Suppose a university were to set out deliberately to improve the mental capacities of its students. Suppose they further claimed that not only could they achieve this but that their students would be more intelligent and mentally alert than any in history. We might be sceptical but if the claims could be sustained should we be pleased?"

His answer is an unequivocal yes. He concludes that it is unethical to stop healthy people taking Ritalin to enhance their mental performance.

But in total disagreement, Professor Anjan Chatterjee from the University of Pennsylvania argues in the BMJ that there are too many risks. In the US, the drug carries a "black box" warning, the most serious, because of its high potential for abuse, serious adverse risks on the heart and the risk of sudden death.

He adds that there are cognitive trade-offs in taking Ritalin, with a loss of creativity, and points out that "being smarter does not mean being wiser". He raises the spectre of children at top preparatory schools taking Ritalin in "epidemic proportions" and pilots, police and doctors being pressurised to take it when on-call.

Progress often carries risk, says Professor Harris. The development of "synthetic sunshine" (firelights, lamplight and electric light) could have forced people to work through the night. The answer was not to ban it but to introduce laws to regulate working hours. "The same is or will be true of chemical cognitive enhancers," he concludes.

A stimulating debate: The pills in question

Ritalin

A stimulant drug introduced in 1956 for the treatment of Attention Deficit Hyperactivity Disorder (ADHD) in children, it has become increasingly widely used, especially in the US. In recent years, reports have emerged of it being abused by students seeking aids to help them through their exams.

Amphetamines

The stimulant was first synthesised more than a century ago and has been used and abused to boost energy, increase wakefulness and prolong endurance. Its users have been as diverse as long distance lorry drivers wanting to ward off drowsiness and women trying to lose weight. Today it is prescribed for ADHD and narcolepsy, and has been investigated for its role in helping stroke victims re-learn motor skills.

Donepezil

Scientists in aviation medicine and in the military have been examining medicines which might increase alertness and concentration to minimise risk of pilot error and maximise endurance. Donepezil, used to treat of dementia, has been shown to boost the performance of pilots on flight simulators, especially in emergencies.

Modafinil

Modafinil, a drug used to treat the sleep disorder narcolepsy, has also been tested on pilots and other members of the armed forces. While commercial pilots have strict rules governing flying time and rest periods, fighter pilots may be called to action at a moment's notice. Tests on helicopter pilots flying on simulators who had been deprived of sleep showed the drug boosted performance.