Processing Speed in Girls with and without ADHD: Association with Longitudinal Outcomes in Symptoms and Academic Achievement

Theoretical models of ADHD often implicate executive function difficulties, particularly inhibitory control, as underlying ADHD symptoms. However, this theory has been challenged by studies showing that only a portion of children with ADHD have deficits in executive function. Processing speed has been suggested as a cognitive endophenotype of ADHD due to shared genetic and neurobiological etiologies with relevant symptom patterns. Indeed, children with ADHD often demonstrate slower processing speed than comparison children. It may be that “lower order” cognitive deficits in processes such as processing speed are crucial with respect to the long-term impairments of children with ADHD.The purpose of the present investigation was to examine (1) processing speed differences between ADHD presentations, (2) the relation between processing speed and ADHD symptomatology, (3) the relation between processing speed and academic achievement, and (4) the relation between processing speed and adult educational and occupational outcomes in a sample of girls with ADHD and their typically developing counterparts.The present study comprises secondary data analysis from 228 participants in a longitudinal investigation of females with and without ADHD (i.e., combined or inattentive presentations). Girls participating in the original study were between the ages of six and 12 years and participated in summer enrichment programs. In addition to the original data collection, three follow-up studies were conducted at five-year, 10-year, and 16-year follow-up intervals, with excellent subject retention, during which participants, caregivers, and teachers completed evaluations, including objective tests of academic performance.In conclusion, findings from the present study demonstrate an association between processing speed and concurrent inattentiveness in girls with ADHD. These findings also demonstrated a long-lasting association between slow processing speed in childhood and poor math performance from childhood through adulthood regardless of diagnostic status. Aside from the association with inattentiveness, slow processing speed does not seem to put girls with ADHD at particular risk for poor academic outcomes through childhood, adolescence, or adulthood. This may be attributable to sex differences in processing speed, such that females tend to have faster processing speeds than males. Indeed, this may be a protective factor of sorts for girls with ADHD. This may also mean that girls may benefit from targeted intervention in deficits other than processing speed. However, it was found that for all girls, regardless of diagnostic status, slow childhood processing speed predicts poor math performance through childhood, adolescence, and adulthood