Data from the U.S. Department of Education show that the number of those age 6 to 22 who are diagnosed with autism has grown at a much faster rate than those diagnosed with other disorders and disabilities that qualify for an Individualized Education Program.

Psychologists are studying the cause of the skyrocketing rates. "The most common viewpoint is there are not really more cases but diagnosis is much better now, and the definition has been expanded to include a broader continuum," says Gary B. Mesibov, PhD, a psychology professor at the University of North Carolina and director of a statewide autism research and treatment program.