Stunning new figures released today by the Centers for Disease Control show the prevalence of autism spectrum disorders in a sample population of eight-year-old children in 2008 soaring 23% over the prevalence in the same sample in 2006, and a whopping 78% over the number found in 2002. In the new report, one in 88 children was estimated to meet the diagnostic criteria for an autism spectrum disorder in 2008, compared to one in 110 in 2006 and one in 155 in 2002.

The report was based on a survey of medical and other records of children in 14 sites across the United States, whether or not they had received a diagnosis of an ASD. The CDC stressed that the sample was not nationally representative. And it’s not known, the CDC writes, whether these increases reflect increased awareness and better assessment or true increases in the prevalence of ASD symptoms. We asked two of the Child Mind Institute’s psychiatrists to weigh in on what it means.

“It would be a misinterpretation to say that this study shows the number of new cases of autism are on the rise,” says Dr. Michael Milham. “What it highlights is that we were obviously missing kids, and underestimating the magnitude of the problem. It shows the need for a continued focus on better monitoring. We need to be looking deeper for cases that are falling through the cracks.”

There are many limits to this kind of surveillance study—they’re highly dependent on what doctors and other experts decide to include in their charts. But it shows, as does the preponderance of evidence over the last few years, that there are a lot more children than we thought there were somewhere on the spectrum, adds Dr. Ron Steingard.

It’s no surprise that within the sample, two of the groups that showed the largest increase were black and Hispanic children. “Obviously no one was looking carefully enough at these populations,” notes Dr. Steingard.

Another group that showed a particularly large increase was children who meet the criteria for an ASD without also exhibiting cognitive impairment. “A generation ago the only kids who would be diagnosed with autism had what I call autism plus—they also had significant cognitive impairment,” says Dr. Steingard. “Once we understood that you could have the core symptoms of autism without mental retardation, it opened the door to a larger population who still had very important social and interpretive impairment.”

What worries Dr. Steingard is that the study might prompt a backlash—that someone looking to cut funding will use it to make charges of overdiagnosis or misdiagnosis. That would leave people with autism and their families in the lurch. “These kids need intensive interventions to do well, and their families need relief and respite.”

Both doctors note that we need to keep getting better at recognizing autism spectrum disorders, because the earlier the diagnosis and intervention, the better the prognosis.