Attention-deficit/hyperactivity disorder: the impact of methylphenidate on working memory, inhibition capacity and mental flexibility.

Objective: To compare children with attention-deficit/hyperactivity disorder (ADHD), before and after the use of methylphenidate, and a control group, using tests of working memory, inhibition capacity and mental flexibility.

Methods: Neuropsychological tests were administrated to 53 boys, 9-12 years old: the WISC-III digit span backward, and arithmetic; Stroop Color; and Trail Making Tests. The case group included 23 boys with ADHD, who were combined type, treatment-naive, and with normal intelligence without comorbidities. The control group (n = 30) were age and gender matched. After three months on methylphenidate, the ADHD children were retested. The control group was also retested after three months.

Results: Before treatment, ADHD children had lower scores than the control group on the tests (p ≤ 0.001) and after methylphenidate had fewer test errors than before (p ≤ 0.001).

Conclusion: Methylphenidate treatment improves the working memory, inhibitory control and mental flexibility of ADHD boys.