Neuropsychological deficits in relation to symptoms of ADHD: independent contributions and interactions.

The aim of the present study was to investigate possible independent and combined effects of inhibitory control, delay aversion, and RT variability in relation to symptoms of hyperactivity/impulsivity and inattention. A community-based sample of school children (N = 111) completed neuropsychological tasks designed to measure inhibitory control, delay aversion, and RT variability. Behavioral symptoms were measured through parental and teacher ratings of the DSM-IV criteria for ADHD and ODD. The results showed that inhibitory control and RT variability were primarily related to symptoms of inattention rather than hyperactivity/impulsivity. Further, out of the three neuropsychological factors studied, only inhibitory control contributed uniquely to the variance of ADHD symptoms. However, significant interaction effects of delay aversion and RT variability on symptoms of both hyperactivity/impulsivity and inattention were found. This study shows the importance of searching for possible combined effects of neuropsychological factors to learn more about the different pathways that lead to ADHD symptoms in children.