Title: Do Motor Abilities Predict ADHD Symptoms in Preschoolers with FXS?

Background: Attention Deficit/Hyperactivity Disorder (ADHD) is the most commonly diagnosed behavioral disorder in children with approximately 11% of the general population diagnosed with ADHD. Children with FXS and ASD experience higher rates of ADHD symptomatology, with rates in the literature ranging from 40-80%. Motor skills have been identified as a predictor of ADHD outcomes within the general population and have also been found to distinguish between clinical groups such as FXS and FXS+ASD. Thus, motor scores may be a viable predictor for ADHD in high risk populations such as FXS. Additionally, the presence of autism symptoms in FXS have been shown to moderate the severity and presence of ADHD in individuals with FXS. However, the relationship between autism symptoms and motor skills has not been investigated in ADHD and FXS.

Objectives: In the present study, we examined whether motor abilities, moderated by ADOS severity scores, were predictive of ADHD symptomatology in a group of preschoolers with FXS. We then examined whether fine motor and gross motor abilities, also moderated by ADOS severity scores, were predictive of ADHD symptomatology in preschoolers with FXS.

Methods: Participants included 36 preschool aged children with FXS. The Child Behavior Checklist 1½-5 ADHD-DSM subscale raw scores (CBCL) were used to assess the presence ADHD symptoms between 36-60 months of age. Both measures were collected at the same time. Broad motor abilities were measured by the Motor scale standard scores from the Vineland Adaptive Behavior Scale (VABS). Fine Motor and Gross Motor Scales raw scores were also used from the VABS.

Results: Results for the regression model testing broad motor skills predicting ADHD indicated that there were no significant associations between motor and ADHD, and that autism symptom severity did not moderate this association, though the overall model approached significance (p = .105; R² = .172). We followed up with two subsequent models to detect whether fine and gross motor skills individually predicted ADHD outcomes, however, no significant associations were found (p’s > .05).

Conclusions: Study findings suggest that motor abilities may lead to developmental outcomes other than ADHD for preschoolers with FXS. Although neither fine motor nor gross motor was significantly associated with concurrent ADHD outcomes in preschool (i.e., 36 to 60 months), motor development in infancy may contribute to later ADHD outcomes for children with FXS. Future work should delineate early developmental pathways to ADHD and identify developmental outcomes related to early motor abilities in children with FXS.