Effect of methylphenidate on Stroop Color-Word task performance in children with attention deficit hyperactivity disorder.

Attention deficit hyperactivity disorder (ADHD) is a neuropsychiatric syndrome common in the pediatric population. It is associated with multiple nonspecific deficits on neuropsychological tests of executive function, and a beneficial response to pharmacotherapy with methylphenidate (MPH) and other psychostimulants. The Stroop Color-Word task is used empirically as an aid in diagnosis and treatment monitoring of ADHD; however, data on the sensitivity of the Stroop interference score to the effects of MPH are limited. To address this issue, we studied Stroop performance in a cohort of 18 MPH-treated prepubescent boys with ADHD and six healthy controls on and off MPH treatment conditions. MPH significantly improved performance in both groups, with the ADHD participants consistently displaying worse scores than those of controls both on and off MPH. These results suggest that though the diagnostic value of the Stroop task in ADHD remains controversial, it has heuristic value for monitoring clinical responses to MPH treatment. More research is needed to ascertain the clinical significance of our findings and to replicate this relatively small effect in a larger cohort, to determine whether MPH effects on Stroop performance are specific to ADHD symptoms or they generalize to other forms of symptomatology.