Differential effects of methylphenidate on attentional functions in children with attention-deficit/hyperactivity disorder.

OBJECTIVE

To examine the effects of methylphenidate on different attentional functions and behavior in children with attention-deficit/hyperactivity disorder (ADHD).

METHOD

A total of 60 ADHD children aged between 8 and 12 years completed a randomized, double-blind, placebo-controlled, within-subject crossover trial with two doses of methylphenidate (0.25 and 0.5 mg/kg body weight) and placebo. A comprehensive neuropsychological test battery was applied, including tests of alertness and sustained, focused, and divided attention as well as two executive tests, the stop-signal paradigm and a visual set-shifting task.

RESULTS

A linear improvement was identified for both medication conditions in the alertness and focused and sustained attention task, but no significant improvement was found for divided attention. Quadratic trends were found for both executive tasks. Responders defined by behavior ratings did not differ from nonresponders.

CONCLUSIONS

Results indicate that attentional functions are influenced differentially by methylphenidate: intensity-dimension functions are best influenced by higher doses, executive functions by moderate doses, and selectivity-dimension functions by variable doses. In addition, divergent results from behavior rating scales and from attentional paradigms emphasize that clinicians have to decide what constitutes an appropriate clinical response. A more comprehensive assessment of attention may help to find an individually optimal dose for the treatment of attentional dysfunctions.