Inhibitory dysfunction on the Stroop in adults diagnosed with attention deficit hyperactivity disorder

Objectives Individuals with ADHD have exhibited impaired performance on the Stroop paradigm. This study aimed to determine whether this was attributable to verbal information processing and/or response inhibition deficits. Design Participants were clinical referrals for follow-up of ADHD in adulthood and healthy controls. Methods Twenty-six patients diagnosed with ADHD in adulthood and 27 matched normal controls were tested using the Stroop neuropsychological screening test. Verbal processing speed was controlled by creating an Interference condition by subtracting each patient’s result on the Colour condition trial from their respective Colour–Word condition results. Results The ADHD group were significantly slower and less accurate on the Colour, the Colour–Word and Interference conditions. Conclusions The findings suggest that the inhibitory dysfunction of a prepotent response on the Stroop reported in ADHD children and young adulthood is not solely attributable to difficulties with verbal processing speed.