Contrast of medical and nonmedical use of stimulant drugs, basis for the distinction, and risk of addiction: comment on Smith and Farah (2011).

Smith and Farah (2011) presented a scholarly review of critical areas related to their intriguing title "Are Prescription Stimulants 'Smart Pills'?" We contend that they accomplished the main goal of the article, to get the facts straight about possible cognitive enhancement via the nonmedical use of stimulant drugs by individuals without a diagnosis of attention-deficit/hyperactivity disorder (ADHD). At the same time, they justified their main conclusions that (a) individuals are seeking and engaging in nonmedical use of stimulant drugs with the expectations of cognitive enhancement despite uncertainty whether such expectations are valid and (b) on some tasks, there are small average benefits of nonmedical use, but the overall pattern is not clear (e.g., small beneficial effects across most individuals or large beneficial effects only in a few individuals, both of which result in small average effects). We offer comments in 3 areas to amplify key topics mentioned but not emphasized by Smith and Farah: (a) characterization of the cognitive effects of medical use of stimulants to contrast with the cognitive effects of nonmedical use; (b) justification of medical use of stimulants by placement on a normally distributed dimension of behavior rather than categorical diagnosis of ADHD, which varies widely across countries; and (c) evaluation of the potential risks of nonmedical use to individuals and to society (e.g., the likelihood of addiction to stimulant drugs in a small minority of the population) rather than just the potential benefits of cognitive enhancement.