Possible Underlying Mechanisms of Hyperactivity in Children with ADHD

Abstract

Conceptualizations of Attention-Deficit/Hyperactivity Disorder (ADHD) have evolved significantly over the years. Historically, early conceptualizations of ADHD described hyperactivity as the core symptom of the disorder. However, when the third version of the Diagnostic and Statistical Manual of Mental Disorders (DSM) was published (1980), hyperactivity became a specific qualifier of the disorder and was no longer necessary for a diagnosis. Despite this shift in conceptualization of the disorder, there is an abundance of empirical evidence, both recent and historical, supporting the fact that hyperactivity is an enduring and clinically impairing symptom domain in ADHD. Despite having numerous validated instruments available to measure hyperactive behavior, most current models of ADHD are purely neurocognitive in nature and fail to sufficiently account for hyperactive symptoms. The aim of this study was to gain a deeper, more nuanced understanding of hyperactivity in children with ADHD, as many questions remain about the relationships between neuropsychological constructs and hyperactivity. A total of 130 participants with ADHD were enrolled and completed working memory and behavioral inhibition tasks while wearing actigraphs. Results showed that unmedicated children with working memory deficits display significantly higher levels of activity than children without a deficit in this area; however, this relationship was no longer significant after controlling for basic attentional processes. There were no significant relationships between level of hyperactivity and behavioral inhibition. Implications of these findings will be discussed in detail