Methylphenidate
(MPH; Ritalin) is one of the most common treatments for Attention-deficit-hyperactivity-disorder
(ADHD) in children and adults. Currently, it is being prescribed solely for
ADHD and narcolepsy. High prevalence of illicit use of this psychoactive
stimulant (students for example) raises public and professional debates
concerning practical and ethical considerations of cognitive enhancement.
However, no study compared the effect of a single-dose of MPH on adults with
ADHD to its effect on healthy adults, and only a single study has compared it in
children. In this research we compared a group of adults with ADHD to a matched
group of non-ADHD adults in their response to a single-dose of MPH, in two
placebo-controlled double-blind randomized trials. The effect of MPH was
measured through a battery of computerized tasks assessing sustained attention,
working memory, and experience-based decision making. Results of both studies
demonstrate a non-selective enhancing effect of MPH on working-memory and on
measures of sustained attention. However, MPH did not alter decision-making
behavior of either group. We therefore suggest that the cognitive-enhancing
effect of MPH is task specific, and is general rather than ADHD-selective. Our
findings are reviewed together with the children's study mentioned above, which
lends more proof to our claim. We therefore cautiously suggest that MPH may be
beneficial for individuals with an initially low cognitive performance in the
above measures, rather than those strictly diagnosed with ADHD.
