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.