title: Similar developmental trajectories in autism and Asperger syndrome: from early childhood to adolescence.
abstract: OBJECTIVE
  The objective of this study was to chart the developmental trajectories of high-functioning children with autism spectrum disorders (ASD) from early childhood to adolescence using the presence and absence of structural language impairment (StrLI) as a way of differentiating autism from Asperger syndrome (AS).
  
  
  METHODS
  Sixty-four high-functioning children with ASD were ascertained at 4-6 years of age from several different regional diagnostic and treatment centers. At 6-8 years of age, the ADI-R and the Test of Oral Language Development were used to define an autism group (those with StrLI at 6-8 years of age) and an AS group (those without StrLI). Growth curve analysis was then used to chart the developmental trajectories of these children on measures of autistic symptoms, and adaptive skills in communication, daily living and socialization.
  
  
  RESULTS
  Differentiating the ASD group in terms of the presence/absence of StrLI provided a better explanation of the variation in growth curves than not differentiating high-functioning ASD children. The two groups had similar developmental trajectories but the group without StrLI (the AS group) was functioning better and had fewer autistic symptoms than the group with StrLI (the autism group) on all measures across time. The differences in outcome could not be explained by non-verbal IQ or change in early language skills.
  
  
  CONCLUSIONS
  Distinguishing between autism and Asperger syndrome based on the presence or absence of StrLI appears to be a clinically useful way of classifying ASD sub-types.
authors.affiliation: Department of Psychiatry and Behavioural Neurosciences, McMaster University, Canada. szatmar@mcmaster.ca
authors.forename: Peter
authors.initials: P
authors.lastname: Szatmari
authors.forename: Susan
authors.initials: S
authors.lastname: Bryson
authors.forename: Eric
authors.initials: E
authors.lastname: Duku
authors.forename: Liezanne
authors.initials: L
authors.lastname: Vaccarella
authors.forename: Lonnie
authors.initials: L
authors.lastname: Zwaigenbaum
authors.forename: Teresa
authors.initials: T
authors.lastname: Bennett
authors.forename: Michael H
authors.initials: MH
authors.lastname: Boyle
mesh_terms: D000223:Adaptation, Psychological; D000293:Adolescent; D000328:Adult; D020817:Asperger Syndrome / Q000175:diagnosis / Q000453:epidemiology*; D001321:Autistic Disorder / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D007806:Language Disorders / Q000175:diagnosis / Q000453:epidemiology; D008297:Male; D012720:Severity of Illness Index; D019956:Stereotypic Movement Disorder / Q000175:diagnosis / Q000453:epidemiology; D011795:Surveys and Questionnaires