Autism spectrum symptoms in Smith-Magenis syndrome and Williams syndrome: comparisons and contrasts
Autism Spectrum Disorder is characterised by a triad of impairments which involve persistent deficits in social-communication, social interaction, restricted and repetitive patterns of behaviour, interests and activities. These impairments are present from early development and cannot be explained better by levels of intellectual disability.
Most individuals with Smith-Magenis syndrome experience a mild to moderate intellectual disability with many individuals also experiencing several disruptive behaviours that are often seen in Autism Spectrum Disorders. These include strong adherence to routines, stereotypies, self-injurious behaviours and problems with social interaction. Recent research has shown that many individuals with Smith-Magenis syndrome may meet the criteria for an Autism Spectrum Disorder diagnosis at some point in their lives.
Individuals with Williams syndrome also experience an intellectual disability in the mild to moderate range and are often reported to show hypersociability, which can present as uninhibited and indiscriminate social initiation. However, despite this hypersociability, individuals with Williams syndrome often have impairments in verbal communication and understanding social interactions which can cause difficulties with social contact. Evidence of behaviours that are seen in Autism Spectrum Disorders are also observed in individuals who have Williams syndrome including strict adherence to routine, stereotypies and in some individuals a lack of verbal language.
In the current study, the frequency and severity of autism spectrum disorder characteristics was compared in eleven individuals with Smith-Magenis syndrome and fourteen individuals with Williams syndrome. Parents and caregivers were asked to complete the Social Communication Questionnaire (SCQ; Lifetime and Current versions) which is an informant screening tool that is used to identify the presence of symptoms associated with Autism Spectrum Disorder. Higher scores on this measure indicate a greater level of impairment.
Results showed that individuals with Smith-Magenis syndrome scored significantly higher on total lifetime and current Autism Spectrum Disorder symptoms compared to those with Williams syndrome. Males with Smith-Magenis syndrome were found to be more significantly affected, with the majority of males with the syndrome showing high levels of autistic-like traits Individuals with Smith-Magenis syndrome scored particularly highly on the social interaction and communication subscales. Interestingly, there were no significant differences between the two groups with regard to levels of stereotyped and repetitive behaviour.
There were no differences, in terms of degree of intellectual disability, between individuals who scored above or below the cut-off score for Autism Spectrum Disorder. The vast majority of individuals with Smith-Magenis syndrome scored above this threshold, whereas a much smaller proportion of individuals with Williams syndrome achieved this score, indicating fewer autism spectrum disorder characteristics.
In conclusion, while both syndrome groups displayed behavioural signs of Autism Spectrum Disorder, these characteristics were significantly more prominent in individuals with Smith-Magenis syndrome. This suggests that Autism Spectrum Disorder interventions may be beneficial to this group. Although occurring less frequently, some individuals with Williams syndrome did display symptoms of Autism Spectrum Disorder, suggesting that autism-specific interventions may be beneficial to some individuals with the syndrome.