Impulsivity as Early Emerging Vulnerability Factor-Prediction of ADHD by a Preschool Neuropsychological Measure.

Impulsivity, comprising deviations of brain-based bottom-up and top-down control processes, has been regarded as a crucial, early emerging marker of a developmental pathway to attention-deficit/hyperactivity (ADHD) and externalizing disorders. In two independent studies (a cross-sectional study and a longitudinal study), we analyzed the concurrent and predictive validity of a task-based neuropsychological impulsivity measure for preschool children. The sample of Study 1 comprised 102 3-5-year-old children (46% boys). In Study 2, 138 children (59% boys) with elevated ADHD symptoms were recruited and assessed at the ages of 4-5 and 8 years. In both studies, preschool impulsivity was measured by a summary score of neuropsychological tasks on approach motivation and hot inhibitory control. For Study 1, the impulsivity measure was significantly associated with symptoms of ADHD and oppositional defiant disorder (ODD) (χ2(1) = 9.8, p = 0.002; χ2(1) = 8.1, p = 0.004). In Study 2, the impulsivity measure predicted the 8-year-olds' ADHD diagnoses over and above concurrent ADHD symptoms (χ2(1) = 10.0, p = 0.002, OR = 5.0, 95% CI: 1.8-14.0). The impulsivity measure showed good concurrent and predictive validity. The measure can be useful for the early identification of children at risk for developing ADHD and externalizing disorders.