The best established prognostic factors for individual outcome wi thin autism spectrum
disorder are presence or absence of associa ted intellectual disability and language impair-
ment (e.g., functional language by age 5 years is a good prognostic sign) and additional
mental health problems. Epilepsy, as a comorb id diagnosis, is associated with greater in-
tellectual disability and lower verbal ability.
Environmental. A variety of nonspecific risk factors, such as advanced parental age, low
birth weight, or fetal exposure to valproate, may contribute to risk of autism spectrum dis-
order.