Overview

• A quarter of American children identified as autistic by age 8 have the most severe form of the disorder, a new study found.
• The rate of severe autism diagnoses grew from about 3 cases per 1,000 children in 2000 to 5 cases per 1,000 in 2016, according to the study.
• In contrast, the prevalence of milder autism has been rising much more rapidly.
• There are wide racial gaps in the rates of severe autism, with black children having the highest rates.
• The study provides the first solid numbers on the share of U.S. children with the most profound autism and suggests the need to differentiate between mild and severe cases..