LAUSR

To identify sources of phenotypic heterogeneity in attention-deficit/hyperactivity disorder (ADHD) accounting for diversity in developmental/ pathogenic pathways, we examined, in a large sample of youth (N = 354), (a) associations between observed temperamental emotionality at age 3, an electrocortical index (i.e., reward positivity [RewP]) of initial responsiveness to reward at age 9, and ADHD symptoms at age 12, and (b) whether the association between emotionality and ADHD symptoms is mediated by initial responsiveness to reward. Bivariate analyses indicated greater positive emotionality (PE) was associated with enhanced RewP, lower age-9ADHD and lower age-12 inattention (IA). Negative emotionality (NE) was not associated with RewP or ADHD. Mediation analyses revealed the association between PE and hyperactivity/impulsivity (H/I) was mediated by RewP; enhanced RewP was associated with greater H/I. Greater PE was associated with enhanced RewP at a trend level. These effects held accounting for age-9 ADHD, age-12 IA and age-12 oppositional defiant and conduct disorder symptoms. As such, preschool emotionality is associated with adolescent ADHD-H/I symptoms through late childhood initial responsiveness to reward. These relations indicate that individual differences in emotionality and reward responsiveness may be informative for personalizing ADHD interventions.