Neuropsychological functioning and severity of ADHD in early childhood: a four-year cross-lagged study

Children with attention deficit/hyperactivity disorder (ADHD) have poorer neuropsychological functioning relative to their typically developing peers. However, it is unclear whether early neuropsychological functioning predicts later ADHD severity and/or the latter is longitudinally associated with subsequent neuropsychological functioning; and whether these relations are different in children with and without early symptoms of ADHD. This study aimed to examine the longitudinal associations between ADHD severity and neuropsychological functioning among children at high and low risk of developing ADHD. Hyperactive/Inattentive (H/I; n = 140) and Typically developing (TD; n = 76) preschoolers (age 3-4 years) were recruited (BL) and followed annually for 3 years (F1, F2, and F3). Teachers rated the children's ADHD severity and impairment using the Behavior Assessment System for Children-2 and the Children's Problem Checklist, respectively. Parent reports of children's ADHD severity were obtained using the Kiddie-Schedule for Affective Disorders and Schizophrenia - Present and Lifetime version. Neuropsychological functioning was assessed using the NEPSY. In the full sample, there were bidirectional longitudinal associations between neuropsychological functioning and ADHD severity between F1 and F3. Among H/I children, neuropsychological functioning at F1 and F2 predicted ADHD severity at F2 and F3, respectively. In contrast, among TD children the only significant relationship observed was that elevated ADHD symptoms at F2 were associated with poorer neuropsychological functioning at F3. Improved neuropsychological functioning may attenuate ADHD symptoms and associated impairment among H/I children during the early school years. Interventions designed to improve neuropsychological functioning among young H/I children may be beneficial in reducing their ADHD severity.