title: Processing speed deficits in attention deficit/hyperactivity disorder and reading disability.
abstract: The goal of the current study was to test whether deficits in processing speed (PS) may be a shared cognitive risk factor in reading disability (RD) and Attention Deficit/Hyperactivity Disorder (ADHD), which are known to be comorbid. Literature on ADHD and RD suggests that deficits on tasks with a speeded component are seen in both of these disorders individually. The current study examined a wide range of speeded tasks in RD, ADHD, comorbid RD+ADHD, and a control group to test whether RD and ADHD have similar profiles of PS deficits, and whether these deficits are shared by the two disorders. The results suggest that a general PS deficit exists in both clinical groups compared to controls, although children with RD demonstrate greater PS deficits than children with ADHD. Two tests (underadditivity and partial correlations) were conducted to test whether these PS deficits are shared. Since we found that PS deficits were underadditive in the comorbid group and that partialling PS reduced the correlation between RD and ADHD, it appears that PS is a shared cognitive risk factor that may help explain the comorbidity of these two disorders.
authors.affiliation: Department of Psychology, University of Denver, Denver, Colorado, USA. mshanah2@du.edu
authors.forename: Michelle A
authors.initials: MA
authors.lastname: Shanahan
authors.forename: Bruce F
authors.initials: BF
authors.lastname: Pennington
authors.forename: Benjamin E
authors.initials: BE
authors.lastname: Yerys
authors.forename: Ashley
authors.initials: A
authors.lastname: Scott
authors.forename: Richard
authors.initials: R
authors.lastname: Boada
authors.forename: Erik G
authors.initials: EG
authors.lastname: Willcutt
authors.forename: Richard K
authors.initials: RK
authors.lastname: Olson
authors.forename: John C
authors.initials: JC
authors.lastname: DeFries
mesh_terms: D000293:Adolescent; D000704:Analysis of Variance; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology / Q000523:psychology*; D002648:Child; D003071:Cognition; D015897:Comorbidity; D004410:Dyslexia / Q000453:epidemiology / Q000523:psychology*; D005163:Factor Analysis, Statistical; D005260:Female; D006801:Humans; D008297:Male; D008960:Models, Psychological; D011930:Reaction Time; D014796:Visual Perception