Effects of methylphenidate on reward strength in boys with attention-deficit hyperactivity disorder.

OBJECTIVE

To test the hypothesis that methylphenidate reduces thresholds for reward in children with attention-deficit hyperactivity disorder (ADHD).

METHOD

A double-blind crossover design was used in which 16 ADHD boys, aged 8 to 13 years, received methylphenidate on one testing occasion and placebo on another. On each occasion, subjects performed a task that required progressively greater numbers of button presses to earn a fixed monetary payoff.

RESULTS

The "breaking point" above which the hyperactive child was unwilling to continue with the task was significantly higher during drug than placebo trials.

CONCLUSIONS

The results support an assumption that underlies the reward system dysfunction hypothesis of ADHD, and they suggest that reward mechanisms may underlie the therapeutic effects of stimulants observed across a wide range of tasks and settings.