Effects of stimulant medication on neuropsychological functioning in young adults with attention-deficit/hyperactivity disorder

Objective: The main goal of this study was to evaluate the impact of stimulant medication on executive function deficits in a group of adolescents and young adults with attention-deficit/hyperactivity disorder (ADHD; DSM-III-R criteria). Method: Male and female subjects aged 15 to 25 years were divided into 3 groups: subjects with ADHD treated with stimulants who took their medication at the time of testing (ADHD active stimulant treatment: N = 26), subjects with ADHD who had not taken stimulant medication in the past month (ADHD no stimulant treatment: N = 94), and non-ADHD control subjects (controls: N = 133). The neuropsychological battery assessed domains of cognitive functioning known to be relevant in ADHD, including tests of executive functions and learning and memory. Data were collected from July 1998 to April 2003. Results: The ADHD no stimulant treatment group had significantly lower aggregate scores compared with the controls for the total aggregate, working memory, interference control, processing speed, sustained attention, and verbal learning domains (all p < .001). The ADHD active stimulant treatment group had significantly poorer scores on the total aggregate (p = .002), interference control (p < .001), and processing speed (p = .003) domains compared with the controls. The ADHD active stimulant treatment subjects scored significantly higher on the domains of sustained attention (p = .04) and verbal learning (p = .03) compared with the ADHD no stimulant treatment subjects. Conclusions: Our study showed that subjects with ADHD who took stimulant medication had higher neuropsychological measures of attention compared with subjects with ADHD who did not take stimulant medication, but differences were not found for other measures of executive function.