Predictors of outcome among high functioning children with autism and Asperger Syndrome

P.Szatmari, S.E. Bryson, M.H. Boyle, D.L. Streiner and E.Duku Journal of Child Psychology and Psychiatry, 44:4 (2003), pp 520-528.

Background: The objective of this paper is to access the extent to which measures of cognitive abilities taken in an inception cohort of young high functioning children with autism and Asperger's Syndrome predict outcome roughly two and six years later. Method: Children who received a diagnosis of autism or Asperger's Syndrome (AS) and who had a nonverbal IQ score in the 'non-retarded' range were included in the inception cohert. Measures of language and non-verbal skills were taken when the children were 4-6 years of age and outcome assessments were completed when the children were 6-8 and 10-13 years of age. The three outcome measures consisted of scales of adaptive behaviours in socialisation and communication and a composite measure of autistic symptoms (abnormal language, abnormal body and object use, difficulties relating to others, sensory issues, and social and self-help difficulties). Results: The explanatory power of the predictor variables were greater for communication and social skills than for autistic symptoms. The power of prediction was stable over time but did differ by PDD subtype. In general, the association between language skills and outcome was stronger in the autism group than in the AS group. Conclusion: These results support the emphasis of early intervention programmes on language but more work needs to be done on understanding variables that influence outcome in social skills and autistic behaviours, particularly in those with AS.

An important clinical implication of these data is that the distinction between autism and AS may be useful in terms of suggesting that working on language skills may improve outcome more dramatically in children with autism than in children with AS. However, it is possible that language is a marker for another, more fundamental, variable that would have a stronger influence on outcome.

The whole notion that AS is a mild form of autism is overly simplistic, as demonstrated by the greater significance of the interactive terms relative to main effect of diagnosis in these analyses. The design employed here cannot address the issue of 'same' or 'different'. Rather it does support our model that AS and autism represent different, but potentially overlapping, developmental trajectories that are influenced by similar (though not identical) prognostic factors. According to this model, children with PDD appear undifferentiated in infancy, but those who develop fluent language by 3 years of age (and so receive a 'diagnosis' of AS) start off on a different developmental pathway than those children who are still nonverbal at that age. As a result, the predictive ability of language in the AS group is limited compared to the autism group. There is an opportunity for children with autism to join the developmental pathway of the AS children once they too develop fluent language, but the longer it takes them to do so, the less likely that is to occur.