About Autistic Spectrum Disorders

The autism spectrum, also called autistic spectrum disorders (ASD) or autism spectrum conditions (ASC), is a spectrum of psychological conditions characterized by widespread abnormalities of social interactions and communication, as well as severely restricted interests and highly repetitive behavior.

The three main forms of ASD are autism, Asperger syndrome, and PDD-NOS. Autism forms the core of the autism spectrum disorders. Asperger syndrome is closest to autism in signs and likely causes. Pervasive developmental disorder not otherwise specified (PDD-NOS) is diagnosed when the criteria are not met for a more specific disorder. Some sources also include Rett syndrome and childhood disintegrative disorder, which share several signs with autism but may have unrelated causes. Unlike autism, Asperger's has no significant delay in language development.

The terminology of autism can be bewildering, with autism, Asperger's and PDD-NOS sometimes called the autistic disorders instead of ASD, whereas autism itself is often called autistic disorder, childhood autism, or infantile autism. ASD, in turn, is a subset of the broader autism phenotype (BAP), which describes individuals who may not have ASD but do have autistic-like traits, such as avoiding eye contact.