Inhibition in ADHD, aggressive, and anxious children: a biologically based model of child psychopathology.

In this study the stop signal task was employed to investigate inhibitory control in 15 children with attention deficit hyperactiviiy disorder (ADHD), 18 aggressive and 20 anxious children, and a group of 17 normal controls. The psychopathological groups were recruited from special educational services. Parent, teacher and child questionnaires were used to select children with pervasive disorders. Controls attended regular classes and scored low on all questionnaires. Based on Quay's model of child psychopathology (Quay, 1988, 1993), we hypothesized a deficit in inhibitory control in children with externalizing disorders, whereas anxious children were predicted to be overinhibited. The ADHD group and the aggressive group showed poor inhibitory control and a slower inhibitory process. No evidence of overinhibition was found in anxious children.