Executive functioning in adult attention-deficit hyperactivity disorder

The present study examined the executive abilities of 35 adults diagnosed with Attention-Deficit Hyperactivily Disorder (ADHD) and 32 adults without the disorder (n = 67) who were equivalent in age, gender, years of education, and Full Scale IQ. The ADHD group performed significantly worse on Stroop Color-Word (eta(2) =.18) and Interference (eta( 2) =.08), as well as time to complete Trails B (eta(2) =.08) than the controls (all ps <. 05). Analysis of Design Fluency indicated that the ADHD group committed more perseverative (eta(2) =.06) and non-perseverative (eta(2) =.12) errors than did controls; however, novel output was equivalent for the groups. No group differences were observed on tests measuring cognitive initiation, abstract thinking, or working memory (all ps >.30; eta(2) =.00-.01). The distributions of WCST variables showed severe skew associated with high-functioning performance on the test among both groups. The pattern of results suggests the presence of specific deficits in response inhibition, with intact abilities in other cognitive domains, such as primary verbal and visuospatial skills. These findings are consistent with the literature on neuropsychological deficits among children with ADHD. That persons with ADHD present a primary deficit of behavioral inhibition supports Barkley's (1997) theory of ADHD, as opposed to theories by Denckla (1996) and Roberts and Pennington (1996) that emphasize intention and working memory.