Autistic spectrum disorder (ASD) is a complex disorder of the central nervous system, which often first appears as delayed speech in children around 18 months of age. The disorder exists at birth and can usually be reliably diagnosed by the time the child is three years old.
Autism is one type of ASD that appears in early childhood — usually before age three. About 15 to 20 children in every 10,000 children are autistic. Boys are up to four times more likely to develop autism than girls.
Children with ASD develop normally into adults. However, they continue to have impaired social communication, interaction and fondness for repetitive actions. How the child turns out is usually determined by his or her cognitive and social abilities.
About 70% of children with ASD are mentally retarded, with most requiring supervision at home and work. They enjoy a normal life expectancy, although some will have residual psychological problems (anxiety and depression) or seizures.
Autism may improve with appropriate education and therapy or as the child matures. Some eventually lead normal or near-normal lives, although they continue to show some social awkwardness.