The range of symptoms varies from person to person and can be mild to severe. The exact incidence of autism is unknown. According to the Autism Society of America, it affects about one out of every 500 children to some degree. It's four times more common in boys than in girls. There are no medical tests for autism.
Doctors make the diagnosis from observation of symptoms and developmental tests.
Once a diagnosis is confirmed, experts recommend intensive early intervention programs. Doctors don't know what causes autism. In some cases it runs in families. Sibilings of children with autism have up to an eight percent chance of also being diagnosed with the condition. Ellen Bolte, a mother of an autistic child had a theory that symptoms may be triggered by some type of bacteria that produces a brain-damaging toxin.