What Is Autism Spectrum Disorder?

Autism spectrum disorder (ASD) is characterized by:

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, while others are severely disabled. The latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) no longer includes Aspergers syndrome; the characteristics of Aspergers syndrome are included within the broader category of ASD.

Information on ASD can also be found on the Eunice Kennedy Shriver National Institute of Child Health and Human Development website and the Centers for Disease Control and Prevention website.

Scientists don't know the exact causes of autism spectrum disorder (ASD), but research suggests that both genes and environment play important roles.

Genetic factors

In identical twins who share the exact same genetic code, if one has ASD, the other twin also has ASD in nearly 9 out of 10 cases. If one sibling has ASD, the other siblings have 35 times the normal risk of also developing the disorder. Researchers are starting to identify particular genes that may increase the risk for ASD.

Still, scientists have only had some success in finding exactly which genes are involved. For more information about such cases, see the information below about Fragile X syndrome and tuberous sclerosis.

Most people who develop ASD have no reported family history of autism, suggesting that random, rare, and possibly many gene mutations are likely to affect a person's risk. Any change to normal genetic information is called a mutation. Mutations can be inherited, but some arise for no reason. Mutations can be helpful, harmful, or have no effect.

Having increased genetic risk does not mean a child will definitely develop ASD. Many researchers are focusing on how various genes interact with each other and environmental factors to better understand how they increase the risk of this disorder.

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NIMH Autism Spectrum Disorder