age < 18 months, (2) a diagnosis of Rett syndrome or Childhood Disintegrative Disorder and (3) evidence of any psychiatric and neurological conditions including: birth anoxia, rubella during pregnancy, fragile X syndrome, encephalitis, phenylketonuria, tuberous sclerosis, Tourette and West syndromes. Subjects with these conditions were excluded based on parental interview and chart review. However, participants with a co-occurring diagnosis of semantic-pragmatic disorder (due to its large overlap with PDD), attention deficit hyperactivity disorder (seen in a large number of patients with ASD during development), and idiopathic epilepsy (related to the core syndrome of ASD) were eligible for the study.
