Onset is most frequently noted between three and four years of age. Frequently the onset is preceded by periods of irritability, increased activity level, and anxiety. This disorder is most frequently noted in males. Profiles in psychological testing will often show an extreme pattern of strengths and weaknesses. This is present even in cases where mental retardation is also present.
Symptoms first appear before the age of three years.
Generally the diagnosis will be based upon behaviors that are exhibited after the age of two years because of the subtle manifestations of Autistic Disorder during infancy. This disorder is most frequently noted in males. Intelligence is most frequently in the normal range, but will sometimes be as low as borderline. No delays are noted in language development, cognitive development, or areas of adaptive behavior, with the exception of social behaviors. The disorder will most likely will be diagnosed in adolescence or as a young adult.