ABSTRACT
BACKGROUND: A substantial proportion of children with attention-deficit/hyperactivity disorder (ADHD) show deficits on inhibitory control tests. However, questions remain about (i) the extent of these deficits across different inhibitory domains, (ii) their relationship to deficits in non-executive processes and (iii) whether they extend into adolescence. METHODS: Seventy-seven children and adolescents with ADHD and 50 non-ADHD controls completed three inhibitory tasks, a simple two choice RT task (2CR) and an IQ assessment. RESULTS: ADHD was moderately associated with deficits on all tasks (effect sizes d=0.5-0.9). Deficits were equally marked in childhood and adolescence. Inhibitory deficits were not associated with IQ and, although reduced substantially, remained significant after performance on a simple reaction time task was controlled for statistically. DISCUSSION: In highlighting the significant, but limited, role of inhibitory deficits in ADHD, these results are consistent with recent accounts that emphasize the neuropsychological heterogeneity of this condition.
