Contrasting cognitive deficits in attention deficit hyperactivity disorder versus reading disability.

Abstract

We compared 2 common and sometimes comorbid developmental disorders, reading disability (RD) and attention deficit hyperactivity disorder (ADHD), in 2 cognitive domains, phonological processes (PP) and executive functions (EF). Subjects were 70 boys of early school age, studied by means of a 2 (RD vs. no RD) × 2 (ADHD vs. no ADHD) × 2 (domain type) mixed-model design. The 2 RD groups (RD-only and RD plus ADHD) were significantly impaired compared with both the control and ADHD-only groups on a PP composite score but performed normally on the EF composite score. The ADHD-only group had an opposite profile and was significantly different from both RD groups and from controls on the EF composite score. Thus, there was a double-dissociation between the RD-only and ADHD-only groups. The comorbid group resembled the RDonly group, consisttent with the hypothesis that their ADHD symptoms are secondary to RD