STEVE INSKEEP, host:
And we're going to hear now about a new autism study that surprised even the people who've been tracking it for years. The number of children diagnosed with autism keeps going up, but it's not clear if that's because autism is becoming more common or because parents, teachers and researchers have become better at identifying it. So researchers set out to find every child with autism in a single community.
NPR's Jon Hamilton reports that those researchers came up with a number that is higher than anybody expected.
JON HAMILTON: Most efforts to identify children with autism focus on kids in special education classes, or those known to have language or learning problems.
Roy Richard Grinker, of the George Washington University, is part of a group who thought this approach might be missing a lot of kids on the autism spectrum.
Professor ROY RICHARD GRINKER (Anthropology, George Washington University): What we wanted to do was to go beyond that and pick a medium-sized city where we could look at every child.
HAMILTON: The city they chose is not in the U.S. It's Goyang in South Korea, not far from Seoul. Grinker says it's an ideal place for this kind of study because the government makes sure every child goes to school. But he says South Korean officials and educators had thought autism was quite rare. The group's five-year study of 55,000 children from seven to twelve showed otherwise.
Prof. GRINKER: We found a prevalence of 2.64 percent. That is two-and-a-half times what the estimated prevalence is in the United States.
HAMILTON: Grinker says the South Korean study probably produced such a high figure because it screened and then tested a whole lot of kids who seemed to be doing OK.
Prof. GRINKER: Two-thirds of the children with autism that we ended up identifying were in mainstream schools - unrecognized, untreated.
HAMILTON: The team of Korean and American scientists who carried out the study say the result doesn't mean there's something different about South Korean children. Bennett Leventhal of New York University Medical Center is one of the study's authors.
Professor BENNETT LEVENTHAL (New York University Medical Center): There's no reason to think that South Korea has more children with autism than anyplace else in the world. What it really tells us is if you really go look carefully amongst all children everywhere, you find that things are far more common than you previously expected.
HAMILTON: But did Leventhal really think that one in every 38 kids in South Korea was on the spectrum?
Prof. LEVENTHAL: No.
HAMILTON: Neither did his wife, Young-Shin Kim of Yale University. She is the study's first author and was born in South Korea.
Ms. YOUNG-SHIN KIM (Yale University): I had some expectation that it's going to be a little higher than the previous studies because we're including children from the general population that were understudied in the past. But the extent - that was a surprise to us.
HAMILTON: Kim says many of the children were probably missed because they didn't misbehave and they weren't failing academically.
Ms. KIM: These children could function at a level that was expected to do, even though they were having a lot of difficulties with their peers and social engagement.
HAMILTON: Also, Kim says, autism carries a severe stigma in South Korea, so some parents may have ignored telltale behaviors. And she says many were upset to learn that they had a child on the spectrum.
Ms. KIM: Some of the parents were yelling at us, like, you guys are crazy. My child is OK and getting really angry about it. Some of the parents were shocked. Some are devastated. But some are like, oh, my God, now it makes sense. Actually, I'm so happy that, actually, you told me that because I couldn't make any sense out of my child.
HAMILTON: The authors say maybe we shouldn't be so surprised that autism is so common. After all, brain disorders like depression and anxiety occur in several percent of the population as well. And Leventhal says the implications of this study are global. He says there are good reasons to identify all kids with autism, even if they aren't failing in school.
Prof. LEVENTHAL: They're socially awkward and they have trouble making friends. They get in trouble because their behavior is a little odd. And then when we teach them their skills, they actually can fit in better and succeed better. Is it perfect? No, but it's better that not.
HAMILITON: The new study appears in the online edition of the American Journal of Psychiatry.
Jon Hamilton, NPR News.