Autism is a complex brain disorder that inhibits a person's ability to communicate and develop social relationships. It is often accompanied by extreme behavioral challenges. In childhood, social interaction, language used in social communication, and imaginative play are impaired. About one in 100 children suffer from the disorder.

International classifications of diseases such as ICD-10 and DSM-IV classify autism as a neurodevelopmental disorder. Diagnosis is determined on the basis of three behavioral impairments or dysfunctions:

• impaired social interaction
• impaired communication
• restricted and repetitive interests and activities.

Twin studies have long indicated a strong genetic influence for autism. Recent research has begun to identify an area of chromosome 11 (11p) and one of a number of genes (Neurexin1) that may be implicated in the development of the disorder.