Influence of IQ and Age in Childhood Autism: Lack of Support for DSM-IV Asperger's Disorder

Children with clinical diagnoses of autism or Asperger's disorder who had normal (n = 47) versus below normal (n = 110) intelligence were compared on several variables, including frequency and types of autistic symptoms, discrepancy between nonverbal and verbal IQs, and degree of incoordination, anxiety, and depression. Children with low versus high IQs had more autistic symptoms overall and a greater percentage of social problems. However, when the effects of IQ and age (and, therefore, mental age) were statistically removed, these differences were no longer significant. This finding does not support the DSM-IV's use of normal cognition as one criterion for creating two distinct diagnostic subgroups (Asperger's disorder and autistic disorder) because differences between children with normal versus below normal cognition can be explained simply by differences in IQ and age (as opposed to some intrinsic differenence related to autism).