Development of ADHD: Etiology, Heterogeneity, and Early Life Course

The Developmental Unfolding of ADHD Symptoms from Early Childhood Through Adolescence: Early Effects of Exuberant Temperament, Parenting and Executive Functioning

Temperament, parenting, and executive functioning (EF) are individual and contextual factors that have been identified to play a role in the development of Attention-Deficit/Hyperactivity Disorder (ADHD) symptoms. Specifically, exuberant temperament in toddlerhood has been associated with both adaptive and maladaptive outcomes, including ADHD symptoms. Therefore, it is important to understand factors that predict which exuberant children experience increased ADHD symptoms and the specific mechanisms through which early exuberant temperament impacts later ADHD symptoms. Using a multi-method, prospective longitudinal design, this study examined a moderated mediation model wherein the interactive effects of observed exuberance and parenting at age 3 predicted the development of parent-reported ADHD symptoms from childhood through adolescence (age 5, 7, 9, 12, and 15) via child EF (i.e., inhibitory control) at age 4. Parent-child dyads (n = 291) from a longitudinal study on child temperament were included. A piecewise model of ADHD symptom growth demonstrated stability in ADHD symptoms from age 5-9 and a decrease from age 9-15. Results support a moderated mediation model wherein an increase in ADHD symptoms throughout childhood was predicted from early childhood exuberant temperament by way of EF, but only for children whose parents displayed less directive parenting. Findings suggest identifiable early markers of risk, including temperament, parenting, and EF- pointing to possible targets for early intervention/prevention.

Eye-movement indices of arousal predict ADHD and comorbid externalizing symptoms over a 2-year period

Attention-deficit/hyperactivity disorder (ADHD) follows a variable course across childhood. Disrupted arousal has been hypothesized to underlie core symptoms as well as comorbid internalizing and externalizing conditions. The current study examined eye-movement and pupil-dilation metrics indexing arousal as longitudinal predictors of ADHD, externalizing, and internalizing symptoms over a 2-year period. Participants aged 8-13 years (N = 54, 30% with a diagnosis of ADHD) completed a modified version of the gap-overlap task including arousal-inducing auditory warning signals. Parents rated symptoms at the time of testing and at 2 years follow-up. Phasic alerting (reaction-time reduction after alerting cues) is an index of arousal. Here, larger phasic alerting effects predicted higher ADHD-symptom levels 2 years later. Blunted pupil-dilation responses predicted externalizing symptoms at T2, controlling for ADHD and externalizing at T1. Our results support the theory that ADHD is associated with altered arousal. Blunted arousal reactivity may be a longitudinal risk factor for externalizing problems in children with ADHD symptoms.