Dec. 18, 2009 – Autism disorders increased by 57% in just four years, the CDC today reported.

By the end of 2006, one in 110 U.S. kids had an autism disorder diagnosed by age 8: one in 70 boys and one in 315 girls, reflecting a nearly fivefold higher risk for males.

The new CDC estimate of autism prevalence, obtained from analysis of child evaluation records in 11 states, is virtually identical to autism numbers reported for 2007 from a huge telephone survey reported last October.

Are today's kids really more likely to have autism, or are doctors and parents just getting better at recognizing this family of developmental disorders?

"At this point it is hard to say how much is a true increase and how much is improved identification," CDC behavioral health scientist Catherine Rice, PhD, said at a news conference. Rice is the lead author of the CDC report.

Rice admits that no single factor or simple explanation can account for the increase. And advocates for autism research say the size and rapidity of the increase can't be explained away.

"Two decades ago we were looking at a prevalence of one in 5,000 children. Now we're looking at one in 100. That really is a staggering increase," Geraldine Dawson, PhD, chief science officer of advocacy group Autism Speaks, tells WebMD.

Dawson said the new numbers justify a huge increase in federal spending on research and treatment.

"The question is what will it take for the federal government to begin to respond to this crisis," Dawson says. "President Obama during the election campaign made a promise that there would be a billion dollars spent every year on finding the causes of autism. We feel that this kind of data coming from a CDC study really requires that level of response."

Rice expressed similar concern.

"The CDC considers autism spectrum disorders to be a significant public health issue," she said. "This report underscores the need for a coordinated and strong response to improve lives of people with ASDs."