Autism is a complex developmental disorder that begins in childhood, usually before the age of three, and lasts throughout a person's lifetime. It is common, affecting approximately one in ninety children born in the United States. In particular, autism affects the parts of the brain that control social interaction and communication. Autism affects people in a wide range of ways. In other words, a person may be affected very mildly or quite severely, and the symptoms may be different from person to person.