Estimates can be funny things because usually they're brought up by people with agendas rather than people interested in objective analysis.  Some estimates in competitive sports put athletic doping usage at 95%, for example, which sounds ridiculously high unless your slippery slope meter works overtime.

What about academia?   The non-medical use of methylphenidate and amphetamine is as high as 25% on some US college campuses, particularly in colleges with more competitive admission criteria, says Vince Cakic of the Department of Psychology at the University of Sydney.  And the use of smart drugs - "nootropics" - to boost academic performance is increasing.

Nootropics were designed to help people with cognitive problems, such as dementia and attention deficit disorder, but students with a looming deadline have several options: modafinil (Provigil), methylphenidate (Ritalin), and amphetamine (Dexedrine).  For boosting memory retention, there's brahmi, piracetam (Nootropil), donepezil (Aricept) and galantamine (Reminyl). And for a bit more zip, there's selegiline (Deprenyl).

Athletes face routine testing for doping.   Will students have to submit blood and urine samples before exams in order to keep the playing field level?

It could happen, says an article in the Journal of Medical Ethics.   And maybe it should.   Everyone recognizes the illegitimacy of chemically enhanced academic performance but these drugs will be near impossible to ban.

"It is apparent that the failures and inconsistencies inherent in anti doping policy in sport will be mirrored in academia unless a reasonable and realistic approach to the issue of nootropics is adopted," Cakic claims.   "As laughable as it may seem, it is possible that scenarios such as this could very well come to fruition in the future. However, given that the benefits of nootropics could also be derived from periods of study at any time leading up to examinations, this would also require drug testing during non-exam periods.

"If the current situation in competitive sport is anything to go by, any attempt to prohibit the use of nootropics will probably be difficult or inordinately expensive to police effectively."

The impact of these drugs is as yet "modest," says Mr Cakic, but more potent versions are in the pipeline. "The possibility of purchasing 'smartness in a bottle' is likely to have broad appeal to students" seeking to gain an advantage in an increasingly competitive world, says Cakic.

But the argument that these drugs should be banned for non-medical use because they confer unfair advantage is rather like suggesting private tuition be banned, contends Mr Cakic. These drugs might even level the playing field for those who have been disadvantaged, he suggests.

The long term safety of smart drugs in healthy people is unknown, and this might prove a good, and perhaps the only, reason to attempt to restrict their use.  Cakic points to the use of caffeine, which is known to enhance sporting performance. It is a form of 'cheating' that is tolerated, he says, because it is relatively harmless.