Users obtain these drugs most
commonly with the aim of enhancing cognition (as opposed
to offsetting sleep deprivation or enhancing
mood). Whilst estimates of the prevalence vary, results
from the United States (14 % of 381 respondents) [6]
and Switzerland (7.6 % of 6275 students), demonstrate
that non-prescription use of prescription only drugs for
the purposes of cognitive enhancement poses a significant
ethical problem.