(ASD). The term “spectrum” refers to the wide range of symptoms, skills, and levels of impairment, or disability, that children with ASD can have. Some children are mildly impaired by their symptoms, but others are severely disabled.
ASD is diagnosed according to guidelines listed in the Diagnostic and Statistical Manual of Mental
Disorders, Fourth Edition - Text Revision (DSM-IV-TR).1 The manual currently defines five disorders, sometimes called pervasive developmental disorders (PDDs), as ASD:

Autistic disorder (classic autism)
Asperger’s disorder (Asperger syndrome)
Pervasive developmental disorder not otherwise specified (PDD-NOS)
Rett’s disorder (Rett syndrome)
Childhood disintegrative disorder (CDD).

This information packet will focus on autism, Asperger syndrome, and PDD-NOS, with brief descriptions of Rett syndrome and CDD in the section, “Related disorders.” Information can also be
found on the Eunice Kennedy Shriver National Institute of Child Health and Human Development
website at http://www.nichd.nih.gov and the Centers for Disease Control and Prevention website at
http://www.cdc.gov/ncbddd/autism/index.html.

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