Two-year outcome of preschool children with autism or Asperger’s syndrome

Szatmari, P., Bryson, S.E., Streiner, D. and Wilson, F. (2000).

Szatmari et al compared the outcome of groups of children with autism or Asperger’s syndrome over a period of two years on variables independent of the defining criteria and identified variables that might account for these differences.

Method: All children 4-6 years of age who came for assessment or were currently in treatment at a pervasive developmental disorder service of one of several centres in a large, geographic region were identified. Children who received a diagnosis of autism (N=46) or Asperger’s syndrome (N=20) on the basis of a diagnostic interview had an IQ in the non retarded ranged were given a battery of cognitive, language, and behavioural tests. Families were contacted roughly 2 years after the date of their enrolment in the study, and may of the tests were re-administered.

Results: Children with Asperger’s syndrome had better social skills and fewer autistic symptoms 2 years after study enrolment than the children with autism. The differences in outcome could not be explained by initial differences in IQ and language abilities. Children with autism who had developed verbal fluency at follow-up were very similar to the children with Asperger’s syndrome at study enrolment.

Conclusions: Although the exact mechanism for the differences in outcome remain to be determined, it appears that Asperger’s disorder and autism represent parallel but potentially overlapping developmental trajectories.

Once children with autism develop a certain level of language fluency, they resemble children with Asperger’s syndrome but at an earlier stage of development. This was demonstrated by our finding that autistic children who were fluent at follow-up were not statistically different from the children with Asperger’s syndrome at the beginning of the study.

The present findings suggest that the differences between Asperger’s syndrome and autism may be largely a matter of timing. The groups seem to be on different but parallel developmental trajectories initially, but there is the possibility that some children with autism may join the trajectory of children with Asperger’s syndrome, once they develop a certain level of fluent language.

The results reported here indicate that the clinical distinction between autism and Asperger’s syndrome does have prognostic importance, although it may be more useful to think of the pervasive developmental disorder subtypes in terms of different developmental trajectories than to argue that they represent different disorders or are on a continuum of severity.