Autism is a severe neurological disorder that causes grave social problems for children. Affected children have trouble communicating and interacting with others. They may not respond to their names or even look at other people. In severe cases, they may become aggressive or injure themselves. Autistic adults who do function socially usually can speak and are viewed as being mildly or subclinically autistic. It cannot be cured, but its symptoms can be treated.
Autism rates reported to authorities is increasing, without apparent cause.
Autism usually appears by age 3, mostly in boys. Studies in the USA and in the UK have established an incidence of about one autistic (psychotic) child per 2,500 births. Since true autism in this sense seems to represent about ten percent of children loosely called autistic, then around one child in 25,000 could be a realistic estimate of classical autism (including mild or subliminal or sub-clinical autism).
Autism rates reported to authorities in California nearly quadrupled between 1980 and 1994, to 208 cases per 100,000 children.
A 1997 study estimated that 80% of the 400,000 autistic people in the USA were also mentally retarded, while a few had IQ's in the genius range.