Abstract
Objective: Executive function deficits have been repeatedly reported in children with Attention Deficit Hyperactivity Disorder (ADHD). Importantly, stimulant medication has been shown to be effective in improving cognitive performance on most executive function tasks. However, neuropsychological tests used to measure executive function in this population have yielded inconsistent results. Methodological limitations, including the use of paper and pencil tasks, may explain these inconsistencies. This study aims to measure executive function in medicated and non-medicated children with ADHD by using a computerised battery, the Cambridge Neuropsychological Test Automated Battery (CANTAB). The CANTAB has previously proved sensitive to executive function deficits in older patients with neurological impairments that are fronto-striatal in nature.
Methods: Executive function was assessed in 66 children with ADHD: 40 were stimulant medication naïve and 26 were treated with stimulant medication. These two groups were compared to 26 age, sex, IQ, education and culture matched controls.
Results: The unmedicated children with ADHD displayed specific cognitive impairments on executive function tasks of spatial short-term memory, spatial working memory, set-shifting ability and planning ability. Impairments were also seen on spatial recognition memory and delayed matching to sample, while pattern recognition memory remained intact. The medicated children with ADHD were not impaired on any of the above executive function tasks except for deficits in spatial recognition memory.
Conclusions: ADHD is associated with deficits in executive function. Stimulant medication is associated with better executive function performance. Prospective follow-up studies are required to examine these effects.