How widespread is 'smart drug' use in the wild?

'Figures published yesterday show that soaring numbers of today’s scholars are abusing prescribed drugs designed to boost concentration in order to keep revising for hours on end,' an article on the Daily Telegraph's website announced last summer. That would be news. Stories about the prevalence of 'smart drugs' tend to be heavy with anecdotes but light on data. They work by suggestion.

And so it turned out once again. The figures themselves were sound. They came from the UK Care Quality Commission's annual report, which noted that 657,000 methylphenidate packages were prescribed in 2012, a rise of 56 per cent since 2007. If more tablets are passing over pharmacy counters, the quantities potentially available for diversion into non-medical use are growing. But this tells us nothing about how much 'scholars' or others are tapping into that potential. The Telegraph article plugged the gaping empirical hole with the assertion that under pressure to get top grades, 'students today will take anything they can get their hands on.'

So, it's tempting to suggest, will commentators writing about the prevalence of 'smart drugs' – journalists and journal authors alike. This isn't just an instance of the media making a mockery of what scientists tell them. The message that comes across from what scientists and other academics say about cognitive enhancers is quite similar to the impression promoted by media coverage: that yet another generation of young people has started up a drug underground, which must surely be intense and widespread even though it is invisible.

Some scholars have argued that it's actually the academics who have supplied the media with the message. Researchers at the University of Queensland linked claims in media stories that 25% of US university students use 'smart drugs' to a figure which has been widely cited in bioethics articles. It came from a study of stimulant use – for whatever reasons, not just cognitive enhancement – in which results from one college indicated that one student in four had used stimulants in the past year. Across all 119 colleges in the study, the rate was just 4.1%.

Equating stimulant use with attempts at cognitive enhancement – despite the long history of amphetamine use by young people for excitement and pleasure – is a common weakness in discussions of how extensive 'smart drug' use may be. Another is reliance on self-selecting respondents. The article that cropped up most often in the media reports examined by the Queensland researchers was one from Nature, reporting the results of a poll in which a fifth of respondents said they had taken drugs to improve their focus, concentration or memory. But surveys like these will tend to attract those who have an interest in the matter, while failing to detain those who don't. As another critical commentary observed, a poll about Vermont vacations wouldn't produce an accurate estimate of the fraction of the population that takes its vacations in Vermont.

In surveys that have inquired about students' motives for taking stimulants, concentration, attention and exams do loom large. The numbers themselves may be modest, though. A study in the German city of Mainz found that 1.5% of school students and less than one per cent of students had used prescription drugs to enhance their cognition; between two and three per cent had used illicit drugs (including cocaine and ecstasy as well as amphetamines) to the same end.

Were these figures a full disclosure, though? When the questions are sensitive, people may not feel even an anonymous questionnaire is anonymous enough. In a subsequent study, the research group used a 'randomized responses technique', a super-anonymization procedure designed to encourage people to answer sensitive questions honestly. Mainz students were asked to think of a birthday, such as their own or their mother's. If it was in the first third of the month, the question they were to answer was whether the date was in the first half of the year. If it wasn't in the first third of the month, they were to indicate whether they had used 'brain-doping' substances in the past year. The researchers thus did not know whether individual respondents had answered the innocuous question or the sensitive one, but they could work out the percentages for the responses as a whole: 20% had said yes to 'brain-doping'.

They also used the same procedure with surgeons attending conferences in Germany, together with a conventional anonymous questionnaire. Answering the questionnaire, 8.9% owned up to having ever used drugs to enhance their cognition. Under the randomized procedure, the figure rose to almost 20%.

The difference between the figures obtained under ordinary anonymity and superanonymity illustrates the uncertainty, and the unease, that clouds all efforts to gauge levels of non-medical drug use. So does the response rate. Although it looks as though randomization has countered bias arising from reluctance to disclose questionable behaviour, the results may not reflect the experience of surgeons as a whole: 3300 were approached but only 1100 responded, which might suggest a 'Vermont vacation' effect.

Of those who answered the questionnaire, three per cent recorded that they had used drugs for cognitive enhancement in the past year. Maybe the rate would have been twice as high, like the lifetime figure, if the question had been asked under the randomized procedure. But even three per cent may count for a lot in a group of professionals who hold people's lives in their hands on a daily basis.