Effects of Methylphenidate on Intelligence and Attention Components in Boys with Attention-Deficit/Hyperactivity Disorder

Abstract

BACKGROUND: Methylphenidate (MPH) is an efficient treatment to reduce behavioral symptoms of attention-deficit/hyperactivity disorder (ADHD); however, its impact on cognitive functioning has not been sufficiently demonstrated so far. This study investigates the hypothesis that MPH improves attention-related cognitive functions. METHODS: Sixty-seven medication-naive boys aged 6-13, with newly diagnosed ADHD, were tested before treatment with a neuropsychological assessment battery, including the Wechsler Intelligence Scales for Children (WISC-IV) and the Test of Attentional Performance for Children (KITAP). A follow-up assessment was performed after 8-12 weeks, with 37 participants receiving MPH treatment and 30 controls without medication. The effect of MPH on test performance was analyzed by repeated measures analyses of variance. RESULTS: Both groups improved significantly across a broad range of psychometric measures of cognitive performance. There were no significant interaction effects of group and time on attention-related cognitive functions. Exploratory analyses revealed an effect of MPH on verbal comprehension in the WISC-IV. CONCLUSION: The study results do not support that MPH improves attention-related cognitive functions of boys with ADHD. The potential effect of MPH on verbal abilities deserves further research.