A neurodevelopmental condition that impairs the way that a person relates to and communicates with other people. Persons with autism also can have unusual behaviors, such as insistence on sameness, obsessions, or stereotypic (purposeless and repetitive) behaviors such as hand flapping, spinning, and toe walking. The condition varies greatly in the presenting symptoms, the timing of presentation, the range and severity of symptoms, and its association with other conditions. While recognition of autism is increasingly common, the cause and the reason for its increase remain unknown. With intensive early intervention, significant improvements in a large percentage of children with autism can be achieved.