Developmental Trajectories of Behavioural Symptoms in ASC

Background:  Although seventy years have passed since Kanner (1943) first described autism, the exact nature of this spectrum of conditions still remains unknown. The failure to develop a full understanding of autism can be partially explained by the continuing lack of information still available on how autism develops over time. There are two main reasons for this neglect. First, the recognition that autism has a strong genetic component has resulted in an implicit tendency to conceptualise autism as a static condition with symptoms that remain pretty stable across time. Second, the major current theories of autism such as Theory of Mind, Executive Function or Weak Central Coherence are heavily weighted towards explanations of primary cognitive deficits, believed to have a genetic origin, and not explanations of developmental interactions between domains of ability/impairment. Yet autism is defined as a developmental disorder and hence any explanation of autism necessarily needs to incorporate a developmental component.

Objectives:  The aims of this study were twofold. First the study aimed to map developmental trajectories of social impairments, repetitive behaviours and sensory behaviours in children with ASC. Second, the study aimed to explore developmental interrelationships between the three areas of impairments.

Methods:  The parents of thirty-six children with ASC aged between 6 and 16 years of age completed the Repetitive Behaviour Questionnaire-2 (RBQ-2; Leekam et al, 2007), the Social Responsiveness Scale (SRS; Constantino and Gruber, 2005) and the Short Sensory Profile. Autism severity was measured by the Childhood Autism Rating Scale, Second Edition (CARS 2; Schopler et al, 2010) in 27 of the children and, for 8 children, it was measured with the Autism Quotient (Auyeung, Baron-Cohen, Wheelwright & Allison, 2008). The protocol for the study received ethical approval from the University of Portsmouth Ethics Committee which follows the guidelines of the British Psychological Society.

Results:  The results showed differential trajectories for each area of behaviour relative to chronological age.  Social difficulties remained relatively stable across the age range. In contrast developmental changes were observed in sensory behaviours, repetitive behaviours relating to Insistence of Sameness and repetitive sensory-motor behaviours. In terms of developmental interrelationships, while the development of social and sensory impairments seem closely linked, the development of repetitive behaviours seems to be relatively independent to the development of impairments in the two other domains.

Conclusions:  The results demonstrate that while some behavioural symptoms change over the life span others remain stable. These findings have important implications for our conceptualisation of ASC. First, the results raise the possibility that while social impairments have a strong genetic component and are therefore impervious to environmental influences, the development of impairments in the two other areas may be successfully influenced by interventions. Second, the possibility that some areas of impairment in autism, in particular Insistence of Sameness, may be a ‘side-effect’ of genetic difficulties in other areas and note core to ASC will also be discussed.