Definitions, Description and Prevalence

Autism is but one developmental disability in the range known as “autism spectrum disorders. ” Other disorders in the autism spectrum include Asperger syndrome, Rett syndrome, and pervasive developmental disorder (PDD). The Centers for Disease Control (CDC) (2007) estimates that cur-rently, about 1.5 million Americans have autism, with the disorder occurring in about 1 of every 150 children overall, and 1 in every 100 boys. While the cause of autism remains unclear, there is some evidence that genetics play at least a partial role; when there is one child with autism in a family, there is a 1-in-20 likelihood that a second child will also have autism—considerably greater than the population likelihood above. Studies of the brain have shown differences between children with autism and those without in certain regions of the brain (CDC, 2007). While the symp-toms of autism can range from quite mild to severe and disabling, there are, in general, certain clusters of behaviors that comprise the autism diagnosis (DSM-IV