Executive functioning : a way to differentiate ADHD/C from ADHD/PI

ADHD is a childhood onset disorder with the cardinal features of inattention, impulsivity, and hyperactivity. Research has verified the validity of two subtypes of ADHD, Inattentive type (ADHD/PI) and Combined type (ADHD/C), which have unique differences in behavioral, emotional, and social impairment. The question remains, however, as to whether the ADHD subtypes actually represent two separate and distinct disorders. Results from studies examining executive functioning ability in ADHD have provided inconsistent and confusing results; however, several studies have shown poorer performance on certain measures of executive function for children with ADHD. Additional research on ADHD suggests that ADHD/PI and ADHD/C may have specific executive functioning deficits. The majority of previous research exploring the executive functioning deficits of ADHD has focused on ADHD/C or has neglected to differentiate between the subtypes, resulting in limited or inconsistent findings. Thus, the exact relationship between executive functioning and the ADHD subtypes is understudied and unclear. This study attempted to identify the differential patterns in the executive functioning of children with ADHD by subtype. Using executive functioning tasks of inhibition, planning, and working memory, this study sought to determine whether children with ADHD/C and ADHD/PI displayed unique patterns of executive functioning. Participants included 60 children aged 8-15 years who were classified into three groups: ADHD/C, ADHD/PI, and control. Results from this study revealed significantly poorer performance by the ADHD subtypes on a task of inhibition. Although analyses using the remaining tasks indicated subtype differences on planning, working memory, and inhibition/ cognitive flexibility tasks, these results were not statistically significant. Results are consistent with previous research which has also detected performance differences by the ADHD subtypes on executive functioning tasks; however, not at the clinically significant level. Analyses examining symptom severity indicated a relation between inattentive symptoms and executive functioning performance. Thus, further exploration into executive functioning within the ADHD subtypes is needed for the clarification of the neuropsychological similarities and differences of these two ADHD subtypes. Such research could assist in the establishment of effective interventions and assessment tools to aid in the earlier and more accurate identification of children with ADHD.