Autism is a general term used to describe a group of complex developmental brain disorders - autism spectrum disorders - caused by a combination of genes and environmental influences. These disorders are characterized, in varying degrees, by communication difficulties, social and behavioral challenges, as well as repetitive behaviors. An estimated one in 88 children in the U.S. is on the autism spectrum - a 78 percent increase in six years that is only partly explained by improved diagnosis.
Autism is a brain development disorder characterized by impaired social interaction and communication, and restricted and repetitive behavior, all starting before a child is three years old. This set of signs distinguishes autism from milder autism spectrum disorders (ASD) such as pervasive developmental disorder not otherwise specified (PDD-NOS).
High-functioning autism (HFA) is an informal term applied to autistic people who are deemed to be "higher functioning" than other autistic people, by one or more metrics. There is no consensus as to the definition. HFA is not yet a recognized diagnosis in the DSM-IV-TR or the ICD-10.
A person with high-functioning autism usually has average or above average intelligence. The differences from other forms of autism have led many psychiatrists to consider high-functioning autism as similar to or the same as Asperger's syndrome. However, the amount of overlap between HFA and Asperger syndrome is disputed. Some researchers argue that the two are distinct diagnostic entities, others argue that they are indistinguishable. (Famous People with Aspergers Syndrome)
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