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Autism Spectrum Disorders Health Center

History of Autism

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What Are the Types of Autism?

Over time, psychiatrists have developed a systematic way of describing autism and related conditions. All of these conditions are placed within a group of conditions called pervasive developmental disorders (PDD). Within PDDs, the autism spectrum disorder (ASD) category includes the following:

Autistic disorder: Children with autistic disorder cannot use verbal or non-verbal communication to interact effectively with others. Usually, children with autistic disorder have severe delays in learning language. They may have obsessive interest in certain objects or information. They may perform certain behaviors repeatedly. To be diagnosed with autistic disorder, symptoms must have been noted before age 3.

Pervasive developmental disorder, not otherwise specified (PDD-NOS): Children diagnosed with "atypical autism" are included in this group. Children with PDD-NOS have symptoms that do not exactly fit those of autistic disorder or any other ASD. For example, the symptoms may have developed after age 3. Or the symptoms may not be severe enough to be considered an autistic disorder.

Asperger's syndrome: Children with Asperger's syndrome may display many of the same symptoms as children with autistic disorder. However, they usually have average or above-average intelligence and initially show normal development of language. They often want to be social with others but don’t know how to go about it. They may not be able to understand others' emotions. They may not read facial expressions or body language well. Their symptoms may not become apparent until school, when behavior and communication with peers become more important.

Other conditions share symptoms with PDDs and ASDs. These conditions include the following:

Rett syndrome: Children with this severe, rare condition begin with normal development from birth through about 5 months of age. However, from about 5 to 48 months of age, head circumference development slows. Children lose motor skills and social interaction and language development become impaired.

Childhood disintegrative disorder: Like Rett syndrome, children begin developing normally. However, from about age 2 to age 10, children are increasingly less able to interact and communicate with others. At the same time, they develop repetitive movements and obsessive behaviors and interests. They lose motor skills, too. This usually leads to them becoming disabled. This autism-like condition is the rarest and most severe in autism spectrum disorder.

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