Academic Achievement in Children with ADHD: the Role of Processing Speed and Working Memory

Academic underachievement is often reported in children with attention-deficit/hyperactivity disorder (ADHD). Research shows working memory (WM), and processing speed (PS) have a predictive role in their academic difficulties. Recent evidence suggests both cognitive functions are related, where slower PS underlies WM deficits. This relationship is not accounted for in the current literature on academic underachievement in children with ADHD. In the current study, the role of PS and WM in the association between ADHD symptom severity and academic achievement is investigated in a sample of 504, 6 to 12 years old children diagnosed with ADHD. Academic achievement is assessed across three subjects (mathematics, reading and spelling), by three measurement methods (standardized tests, parent, and teacher ratings). In addition, the role of PS is investigated in the relationship between ADHD symptom severity and WM. Findings show the association between inattention symptom severity and achievement on all three academic subjects is statistically mediated by PS and WM sequentially. For mathematics and spelling performance, PS was a single mediator in this association. Further, PS statistically mediated the relation between inattention symptom severity and WM performance. Hyperactivity/impulsivity symptom severity predicted mathematics performance directly, but none of the indirect effects were significant. The current results show that PS plays an important role in the academic achievement of children with increased inattention symptoms, as well as the WM deficits often reported in this population. These findings have important implications for theoretical accounts of ADHD, as well as academic interventions, currently focusing primarily on WM deficits.