Study and better diagnostic classification of these children shows that there can be a large range of language ability, intelligence, and social communication ability. The cause of autism is unknown.
Genetic factors are probably to blame.
Despite ideas popular in the past, it is now known that parents do not cause autism in their children. There is no single best treatment for autism and other PDDs. Therapy is both specialized and highly individualized for each child's needs. Early detection and treatment of PDDs is known to improve long term outcome. Children entering treatment under age three do better than those who are not referred for treatment until age 5 or later.