Yesterday, the Centers for Disease Control and Prevention (CDC) raised eyebrows, and concern among current and prospective parents, with a report documenting that the rate of autism spectrum disorder (ASD) diagnosis in the United States jumped 30% between 2008 and 2010 , from one in 88 to one in 68 children. CDC officials don’t know, however, whether the startling increase is due to skyrocketing rates of the disorder or more sensitive screening, or a combination of both. (Forbes gives a nice rundown of the many reasons for this uncertainty ).
The number of diagnoses “have been steadily climbing” from one in 150 since the CDC’s national surveillance system was put into place in 2000, “so I guess I shouldn’t be that surprised” by the new data, says Sarah Spence, a neurologist at Boston Children’s Hospital. About half of the children diagnosed with ASD in the new report had normal or above-average intelligence, compared with a third of children 10 years ago, suggesting that a significant proportion of the new cases are due to more sensitive diagnostic measures rather than increased incidence, she says. Still, “I think all of us in the field are a little frightened by the numbers.”
Huge differences in rates of diagnosis between regions—one in 45 children in New Jersey, compared with one in 175 in Alabama, for example—need to be accounted for before the new data can be properly interpreted, says veteran autism researcher Catherine Lord, a psychologist at Weill Cornell Medical College in New York City. “As a researcher it’s hard to believe” that the increase in cases is as large as the report suggests, she says. “It’s time for the CDC to really put some effort into figuring out why there are these huge discrepancies.”
Nonetheless, the new data suggest that more professionals trained to properly diagnose and treat developmental disorders are desperately needed, Spence says. Advocacy groups have jumped on the new study  to call for more federal funding for research and better services for families affected by the disorder.