The autism spectrum disorders (ASDs) are developmental disabilities that consist of autistic disorder, Asperger syndrome, and atypical autism (also known as Pervasive Developmental Disorder Not Otherwise Specified). All three of these subtypes of autism spectrum disorders are characterized by problems with social interaction and communication.
Young children with any of the autism spectrum disorders often display similar symptoms and it is not until later in life that they can be accurately diagnosed. In addition, little is known about the causes of the autism spectrum disorders, which makes distinguishing between autistic disorder, Asperger syndrome, and atypical autism at the diagnostic level a difficult task.
According to a longitudinal study published in the Journal of Child Psychology and Psychiatry in 2009, the presence or absence of a structural language impairment may be a useful way to distinguish between autism and Asperger syndrome in young children.
A structural language impairment refers to the inability to comprehend and construct sentences with proper grammar. Although children with a structural language impairment may understand the meaning of certain words or phrases, they have difficulty understanding how these words or phrases should be arranged in a sentence.
Sixty-four autistic children in this study were tested for a structural language impairment between six to eight years of age. Three subsequent follow-up assessments were also used to examine the development of these children into late adolescence. By the end of the follow-up period, the oldest of the children were 19-years-old.
The authors of this study found that children who had a structural language impairment were more likely to have more autistic symptoms later in life than children who did not have a structural language impairment, regardless of other factors, such as non-verbal IQ scores.
These results suggest that the presence of a structural language impairment at six to eight years of age may be an indication of autistic disorder, while autistic symptoms in the absence of a structural language impairment may be an indication of Asperger syndrome.
Reference:
Szatmari, P., Bryson, S., Duku, E., Vaccarella, L., Zwaigenbaum, L., Bennett, T. & Boyle, M.H. (2009). Similar developmental trajectories in autism and asperger syndrome: from early childhood to adolescence. Journal of Child Psychology and Psychiatry, Vol. 50, No. 12: 1459-1467.