Autism is classified as one of the pervasive developmental disorders of the brain. It is not a disease. These symptoms can vary in severity. In addition, people with autism often have abnormal responses to sounds, touch, or other sensory stimulation.
Symptoms usually appear during the first three years of childhood and continue through life.
Recent studies strongly suggest that some people have a genetic predisposition to autism. Researchers are looking for clues about which genes contribute to this increased susceptibility. In some children, environmental factors also may play a role. Studies of people with autism have found abnormalities in several regions of the brain which suggest that autism results from a disruption of early fetal brain development. Autism affects an estimated 10 to 20 of every 10,000 people, depending on diagnostic criteria used, and strikes males about four times more often than females.