Defining the motor profile of children with autism, asperger's disorder and attention deficit hyperactivity disorder

Autism, Asperger’s disorder (AD) and Attention Deficit Hyperactivity Disorder- Combined Type (ADHD-CT) are highly prevalent childhood disorders associated with atypical development and behaviour. In May 2013, DSM-5 will be released and will include highly anticipated changes to the current diagnostic criteria for all three disorders, including collapsing autism and AD into an ‘ASD’ category and allowing a dual diagnosis of ASD and ADHD. The change in diagnostic criteria will present new opportunities as well as challenges for understanding the boundaries, similarities, and differences between these disorders. There is an increasing recognition in the literature of understanding non-core symptoms such as motor difficulties in children with neurodevelopmental disorders. The aim of this thesis is to investigate the motor profile of ASD and ADHD in relation to social-emotional symptoms in a bid to better understand the boundaries, similarities, and differences between these disorders. The aim of the first study was to investigate the motor profile of 7-12 year old children with autism and AD using the Movement Assessment Battery for Children (MABC); and the relationship between motor disturbance and social-emotional symptoms. Children with autism and AD were found to differ in overall motor proficiency. Poorer motor performance in the ASD group was shown to be associated with greater social-communicative and emotional-behavioural disturbance. The second study employed a touch screen version of the Fitts’ aiming task to explore upper limb movements in children with autism and AD. Children with autism exhibited more variable and constant error when performing the Fitts’ aiming task compared to the AD and typically developing (TD) groups. The third study employed the Movement Assessment Battery for Children – Second Edition (MABC-2) to investigate motor proficiency in children with ADHD-CT who had been screened for autism. Contrary to past findings, the ADHD-CT group performed in the ‘no movement difficulty detected’ range of the MABC-2. Severity of inattentive symptoms was also found to be associated with greater motor impairment. The fourth study employed a gait paradigm to investigate gait functioning in children with ADHD-CT. Children with ADHD-CT without autism exhibited subtle cerebellar-like timing anomalies during walking, characterised by an increase in cadence in the fast walking condition. The fifth study employed the same Fitts’ aiming paradigm to explore upper limb movements in children with ADHD-CT. Individuals with ADHD-CT produced more variable error compared to the TD control group. Increased variable error was also found to be associated with increased severity of social-communication disturbance. The sixth study employed as simple loops handwriting task to investigate handwriting in children with ADHD-CT without autism. The ADHD-CT group was found to produce larger handwriting (macrographia) compared to the typically developing group. There are two clinical implications stemming from this thesis, (1) although children with autism and AD will now come under the ASD diagnostic category in DSM-5, careful attention is required to understand the unique motor challenges children with autism v AD experience, and (2) ADHD-CT children who are screened for autism, may not experience the same level of motor difficulties as children with comorbid autistic symptoms. The findings of this thesis highlight the importance of understanding the unique motor challenges associated with autism, AD and ADHD in both a categorical and dimensional way.Awards: Vice-Chancellor’s Commendation for Doctoral Thesis Excellence in 2013