Set-shifting in adults with ADHD.

Difficulties related to inhibition and set-shifting have been suggested as possible endophenotypes of Attention Deficit Hyperactivity Disorder (ADHD). However, such difficulties have not been consistently found in studies using standard neuropsychological tests. This has been partly explained by the complexity of these tests and the need to include contrast measures which control for more basic functions. The purpose of the present study was to examine whether difficulties related to inhibition and set-shifting in adult ADHD patients could be revealed by the Color Word Interference Test (CWIT) from the Delis Kaplan Executive Function System (D-KEFS). A clinically recruited group of adults with ADHD (n = 60) obtained significantly lower scores than population derived controls (n = 60) on both primary summary (p < .001) and contrast measures (p = .004) of set-shifting. The differences between the groups remained statistically significant after controlling for intellectual function and working memory (p = .003). However, no significant differences between the groups were observed on any measure of inhibition. The study indicates that adults with ADHD have specific difficulties with set-shifting as measured by the CWIT, difficulties that probably also reflect problems related to executive function in their daily life.