A - 37 ADHD-Related Hyperactivity and Impulsivity: Distinct or Overlapping Dimensions?

Abstract Objective It is debated whether hyperactivity and impulsivity should remain combined within the (DSM) hyperactivity/impulsivity domain or be separated. To address this dispute, we sought to determine whether hyperactivity and impulsivity are differentially related to executive functioning (EF), a common deficit area in ADHD. Method Participants included 120 children (ages 8–11; 89.9% White; 51.6% girls) from a community sample tested in a laboratory setting. To be included, they must have ADHD (59.4%) or be typically developing (40.6%). Hyperactivity and impulsivity scales were created from symptoms from a parent-report Behavior Assessment System for Children and DSM-IV questionnaire, ADHD section. The Behavior Rating Inventory of Executive Functioning (BRIEF) Working Memory scale (WMsc) and the Children’s Memory Scale Picture Locations (visuospatial sketchpad), Numbers Forward (phonological loop), and Sequences (central executive) subtests were used to assess working memory (WM). Inhibition was assessed with the BRIEF Inhibition scale (Isc) and A Developmental Neuropsychological Assessment (NEPSY) Tower Rule Violations (RV). Emotional control (EC) was measured with the BRIEF’s EC scale. Results Confirmatory linear regressions (SPSS Enter method) with all EF measures as IVs revealed Isc and WMsc were significant predictors of impulsivity [F(7,120) = 24.85, p < 0.001]. For hyperactivity [F(7,120) = 21.40, p < 0.001], WMsc, Isc, and RV were significant predictors. Exploratory analyses revealed WMsc was related to hyperactivity in controls but impulsivity in ADHD. Conclusions Similarities and differences were found between hyperactivity and impulsivity in relation to EF. Whereas inhibition was similarly related to hyperactivity and impulsivity, WM’s relationships were dissociable between groups. Hence, further research is needed, including areas affected in ADHD besides EF.