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Autism Spectrum Disorders Health Center

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Understanding Autism -- the Basics

What Is Autism? continued...

Autism is said to be increasing; however, it is not entirely clear whether the increase is related to changes in how it is diagnosed or whether it is a true increase in the incidence of the disease.

The most recent version of the Diagnostic and Statistical Manual of Mental Disorders version 5 (DSM-5) has just a single category for the diagnosis of an autistic disorder-- autism spectrum disorders, which includes the following disorders that were previously diagnosed as individual disorders:

  • Autistic disorder. This is what most people think of when they hear the word "autism." It refers to problems with social interactions, communication, and imaginative play in children younger than 3 years.
  • Asperger's syndrome. These children don't have a problem with language -- in fact, they tend to score in the average or above-average range on intelligence tests. But they have the same social problems and limited scope of interests as children with autistic disorder.
  • Pervasive developmental disorder or PDD -- also known as atypical autism. This is a kind of catch-all category for children who have some autistic behaviors but who don't fit into other categories.
  • Rett syndrome. Children with Rett syndrome, primarily girls, start developing normally but then begin losing their communication and social skills. Beginning at the age of 1 to 4 years, repetitive hand movements replace purposeful use of the hands. Children with Rett syndrome are usually severely cognitively impaired.
  • Childhood disintegrative disorder. These children develop normally for at least two years and then lose some or most of their communication and social skills. This is an extremely rare disorder and its existence as a separate condition is a matter of debate among many mental health professionals.

These disorders may now be diagnosed as either a social communication disorder or autism spectrum disorder based on the primary impairments.

What Causes Autism?

Because autism runs in families, most researchers think that certain combinations of genes may predispose a child to autism. But there are risk factors that increase the chance of having a child with autism.

Advanced age of the mother or the father increases the chance of an autistic child.

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