Do executive deficits and delay aversion make independent contributions to preschool attention-deficit/hyperactivity disorder symptoms?

Objective: To test whether deficits in executive function and delay aversion make independent contributions to levels of attention-deficit/hyperactivity disorder (ADHD) symptoms exhibited by preschool children. Method: One hundred fifty-six children between 3 and 5.5 years old (78 girls and 78 boys) selected from the community completed an age-appropriate battery of tests measuring working memory, set shifting, planning, delay of gratification, and preference for delayed rewards. Parents completed a clinical interview about their children's ADHD symptoms. Results: Analysis of test performance revealed two factors: executive dysfunction and delay aversion. Multivariate analysis demonstrated that when other factors (i.e., age, IQ, and conduct problems) were controlled, executive dysfunction and delay aversion each made significant independent contributions to predictions of ADHD symptoms. Conclusions: Preschool ADHD symptoms are psychologically heterogeneous. Executive dysfunction and delay aversion may represent two distinct and early appearing neurodevelopmental bases for ADHD symptoms.