Study: Autism May Be More Common Than Thought

Researchers Suggest Many Undiagnosed Kids Have Mild Autism

Medically Reviewed by Laura J. Martin, MD on May 09, 2011
From the WebMD Archives

May 9, 2011 - A "startling" one in 38 children has autism, South Korean and U.S. researcher find.

The estimate is far higher than CDC's estimate of one in 110 children, as the study found many school kids have mild, undiagnosed autism.

The elaborate study searched for 7- to 12-year-old children with autism spectrum disorder (ASD) among 55,000 children in a community outside Seoul, South Korea. Largely funded by the advocacy organization Autism Speaks, the study was led by Young Shin Kim, MD, PhD, MPH, of Yale University.

"They came up with the startling number that one in 38 children has an autism spectrum disorder," Geraldine Dawson, PhD, chief science officer for Autism Speaks, tells WebMD. "This raises an important question for the U.S.: How many kids in the general education classroom actually have an ASD but not a diagnosis? These children may have gone under the radar."

"This means that about two-thirds of children with ASD are in the community, unrecognized and untreated. Their lives can be improved significantly with early identification and intervention," Kim said at a news conference.

The new findings do not mean that more children have suddenly come down with autism.

"It seems they have been there all along but were not counted in previous studies," Kim says.

It's the first time a large study has screened a general population for autism. Autism expert Rebecca Landa, PhD, director of the autism center at Baltimore's Kennedy Krieger Institute, tells WebMD in an email that the study methods will have to be validated by future studies. Landa was not involved in the Kim study.

Kim agrees that further studies will have to confirm the current findings. Such studies are underway in India, South Africa, Mexico, and Taiwan.

Study researcher Bennett L. Leventhal, MD, of the NYU Child Study Center, thinks the same study methods would yield similar results in the U.S.

"If researchers went into the grade schools in their communities and looked there, we think they would come up with numbers similar to those we are reporting," Leventhal said at the news conference. "This means there are uncounted children who are not in the services system."

School Kids With Undetected Autism

Who are these uncounted children? When they looked at kids already identified as special-needs children, Kim and colleagues found pretty much the same autism prevalence and the same levels of disability as seen in U.S. and European studies.

The surprise came from the undiagnosed children in the general school population. Some two-thirds of the kids diagnosed with autistic disorder, and 90% of those with other ASDs (such as pervasive developmental disorders) had average or superior intelligence.

"Historically, we thought children with autism were pretty disabled. But intellectual disability isn't the core feature of autism," Gary W. Goldstein, MD, president and CEO of the Kennedy Krieger Institute and professor of neurology and pediatrics at Johns Hopkins University, School of Medicine. Goldstein was not involved in the Kim study but does serve on the board of Autism Speaks.

"The children newly identified in this study are those whose impairment is pretty much limited to the core features of autism: aberrant socialization, lack of communicating with other people in an accepted way, and restricted or repetitive behaviors," Goldstein says.

This suggests that autism and Asperger's syndrome may not be separate disorders, Leventhal says.

"This suggests there is a continuum running from children who are quite impaired to those with relatively mild cognitive and language problems to those who have no cognitive or language problems," he said. "The common variable happens to be difficulties with social process and social function. So drawing a line between Asperger's and ASD might not be as easy as it seemed with earlier criteria."

Regardless of how intelligent they are, how could children with ASD go undetected?

In South Korea, the typical school day lasts 12 hours, five to six days per week. It is a highly structured environment with an emphasis on academics rather than on socialization. The core features of ASD may more easily go unrecognized in such an environment.

U.S. schools are not organized this way. So how could a kid with ASD remain undiagnosed?

"It may be a lack of professionals in a community, or some families not seeking help due to cost, or it may be that some of these kids with ASD function quite well in the classroom setting," Dawson says. "But the same child at noon hour with peers may be socially isolated and awkward in relationships with peers. Having good social skills is absolutely essential for being successful in the real world."

The Kim study appears in the advance online issue of the American Journal of Psychiatry.

WebMD Health News



Kim, Y.S. American Journal of Psychiatry, published online May 6, 2011.

Young Shin Kim, MD, PhD, MPH, Yale University.

Bennett L. Leventhal, MD, NYU Child Study Center.

Geraldine Dawson, PhD, chief science officer, Autism Speaks.

Gary W. Goldstein, MD, president and CEO, Kennedy Krieger Institute; professor of neurology and pediatrics, Johns Hopkins University School of Medicine, Baltimore.

Rebecca Landa, MD, director, Center for Autism & Related Disorders, Kennedy Krieger Institute, Baltimore.

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