The relationship between motor milestone achievement and childhood motor deficits in children with Attention Deficit Hyperactivity Disorder (ADHD) and children with Developmental Coordination Disorder.

BACKGROUND: The prevalence of motor impairment is high in ADHD, but we do not know if this stems from infancy. AIMS: 1) to compare the acquisition of motor milestones across three groups: Typically Developing (TD), Attention Deficit Hyperactivity Disorder (ADHD) and Developmental Coordination Disorder (DCD); 2) to determine the relationship between current motor ability and ADHD characteristics in children with ADHD. METHODS AND PROCEDURES: The parents of children aged 8-16 years (ADHD, N = 100; DCD, N = 66; TD, N = 40) completed three online questionnaires: Motor milestone questionnaire; Developmental Coordination Disorder Questionnaire (DCDQ'07) (concurrent motor ability); Conners 3 Parent Rating Scale Long Form (ADHD characteristics). OUTCOME AND RESULTS: When considered as a group, the ADHD group achieved motor milestones within a typical timeframe, despite concurrent motor impairments. Motor ability was not associated with ADHD characteristics. Latent Profile Analysis demonstrated that 56 % of the ADHD group and 48 % of the DCD group shared the same profile of motor milestone achievement, concurrent motor ability and ADHD characteristics. OUTCOMES AND CONCLUSIONS: Unlike children with DCD, the motor impairment often observed in ADHD is not evident from infancy. It is also not part of the ADHD phenotype. Individual differences analysis demonstrated the broad heterogeneity of the ADHD phenotype.

Cross-Domain Associations Between Motor Ability, Independent Exploration, and Large-Scale Spatial Navigation; Attention Deficit Hyperactivity Disorder, Williams Syndrome, and Typical Development.

In typical infants, the achievement of independent locomotion has a positive impact on the development of both small-scale and large-scale spatial cognition. Here we investigated whether this association between the motor and spatial domain: (1) persists into childhood and (2) is detrimental to the development of spatial cognition in individuals with motor deficits, namely, individuals with attention deficit hyperactivity disorder (ADHD) and individuals with Williams syndrome (WS). Despite evidence of a co-occurring motor impairment in many individuals with ADHD, little is known about the developmental consequences of this impairment. Individuals with WS demonstrate impaired motor and spatial competence, yet the relationship between these two impairments is unknown. Typically developing (TD) children (N = 71), individuals with ADHD (N = 51), and individuals with WS (N = 20) completed a battery of motor tasks, a measure of independent exploration, and a virtual reality spatial navigation task. Retrospective motor milestone data were collected for the ADHD and WS groups. Results demonstrated a relationship between fine motor ability and spatial navigation in the TD group, which could reflect the developmental impact of the ability to manually manipulate objects, on spatial knowledge. In contrast, no relationships between the motor and spatial domains were observed for the ADHD or WS groups. Indeed, while there was evidence of motor impairment in both groups, only the WS group demonstrated an impairment in large-scale spatial navigation. The motor-spatial relationship in the TD, but not the ADHD and WS groups, suggests that aspects of spatial cognition can develop via a developmental pathway which bypasses input from the motor domain.