Behavioral and executive functions in children with Attention-Deficit Hyperactivity Disorder and Reading Disability

Attention, impulse control activity level, and motor decision/response organization were assessed in 70 child psychiatric outpatients, using a continuous performance test (CPT), a solid-state actigraph, and a response incompatibility task. Subjects were divided based on the presence or absence of attention-deficit hyperactivity disorder (ADHD) and/or reading disability (RD). Two-way ANOVAs yielded significant main effects for ADHD, but not RD, on objective measures of impulsivity and overactivity. No significant differences were found on a CPT measure of inattention. The response incompatibility task revealed differential performance between ADHD subgroups with and without comorbid RD. Deficits in motor decision/response organization were observed in the ADHD-only subgroup, but not in the comorbid ADHD+RD subgroup. These findings suggest that children with ADHD, RD and comorbid ADHD+RD have at least partially distinct underlying cognitive and neuropsychological disturbances, and that executive function deficits may be present primarily in ADHD children without RD.