Autism spectrum disorder (ASD) is a developmental disability caused by differences in the brain. It is a neurological disorder that affects the development of the brain, causing difficulty with behavior, communication, learning, and social interaction.
Scientists do not know yet exactly what causes these differences for most people with ASD. However, some people with ASD have a known difference, such as a genetic condition. There are multiple causes of ASD, although most are not yet known.
There is usually nothing about how people with ASD look that sets them apart from other people, but they may communicate, interact, behave, and learn in ways that are different from most other people. The learning, thinking, and problem-solving abilities of people with ASD can range from gifted to severely challenged. Some people with ASD need a lot of help in their daily lives; others need less.
A diagnosis of ASD now includes several conditions that used to be diagnosed separately: autistic disorder, pervasive developmental disorder not otherwise specified (PDD-NOS), and Asperger syndrome. These conditions are now all called autism spectrum disorder.
According to the Centers for Disease Control and Prevention (2014), about one in 68 children in the United States has an ASD. These disorders are among the most common developmental disabilities, after intellectual disabilities and cerebral palsy.