Cross-sectional evaluation of cognitive functioning in children, adolescents and young adults with ADHD.

Attention-deficit/hyperactivity disorder (ADHD) often persists into adulthood, albeit with changes in clinical symptoms throughout the life span. Although effect sizes of neuropsychological deficits in ADHD are well established, developmental approaches have rarely been explored and little is yet known about age-dependent changes in cognitive dysfunction from childhood to adulthood. In this cross-sectional study, 20 male children (8-12 years), 20 adolescents (13-16 years), and 20 adults (18-40 years) with ADHD and a matched control group were investigated using six experimental paradigms tapping into different domains of cognitive dysfunction. Subjects with ADHD were more delay-aversive and showed deficits in time discrimination and time reproduction, but they were not impaired in working memory, interference control or time production. Independent of age, the most robust group differences were observed with respect to delay aversion and time reproduction, pointing to persistent dysfunction in the mesolimbic reward circuitry and in the frontal-striatal-cerebellar timing system in subjects with ADHD. Across all tasks, effect sizes were lowest for adolescents with ADHD compared to age-matched controls. Developmental dissociations were found only for simple stimuli comparison, which was particularly impaired in ADHD children. Thus, in line with current multiple-pathway approaches to ADHD, our data suggest that deficits in different cognitive domains are persistent across the lifespan, albeit less pronounced in adolescents with ADHD.