A disconnect between motor milestone achievement and motor development in Attention Deficit Hyperactivity Disorder; implications for interventions

Attention Deficit Hyperactivity Disorder (ADHD) is the most common neurodevelopmental disorder in childhood. Where studies have investigated motor abilities (balance, ball skills, hand and finger movements), difficulties are reported for this group. Given the importance of motor abilities in everyday life (in social interaction, to produce language, for handwriting and for activities of daily living such as eating), knowledge is surprisingly limited in this area.

We explored the motor system in ADHD in the most detailed study to-date. In line with previous findings, we demonstrated that ~50% of children with ADHD have a substantial motor deficit. We also found that children with ADHD who demonstrate a motor deficit in childhood are not delayed in reaching motor milestones (e.g., crawling and walking) as infants. This suggests that the motor deficit observed in childhood is not present from birth but emerges as a developmental consequence of subtle impairments in infancy. This differs from children with Developmental Coordination Disorder (DCD) who are delayed in reaching motor milestones, which suggests that the motor impairments in DCD are present from birth. We propose to investigate motor milestone achievement in children with ADHD and children with DCD within the same study for the first time. We will collect data via online questionnaires. This is a cost effective way of achieving larger sample sizes than is possible with face-to-face testing sessions.

​If this study demonstrates delayed motor milestone achievement in DCD, but not in ADHD, this raises the possibility that later motor deficits in children with ADHD could be reduced or eliminated through training of the subtle precursors to motor impairment before the impairment emerges. The results of this large-scale proof-of-concept study will feed into our planned future grant application to determine the developmental interactions between the attention and motor domains in infants at risk of ADHD (20% to 40% of children with a sibling with ADHD, present with ADHD themselves). It is crucial to establish the developmental links across different types of behaviour, because it is possible that difficulties in one area (in this case, motor skill in childhood) stem from difficulties in another area (e.g., early attention to motion) that develops earlier in life. Knowledge of the developmental consequences of subtle impairments in infancy in ADHD will enable us to decide when/ how to intervene, to help people with ADHD to achieve their potential in the motor domain. This might, in turn, help with other areas of development.