New federal data indicate that 1 in 88 U.S. children had autism or other autism spectrum disorders in 2008, up from 1 in 110 kids in 2006 and 1 in 150 in 2002.
Although that’s a worrisome trend, reasons for autism’s rising prevalence — measured in nonrepresentative national samples of 8-year-olds — remain unclear. The Centers for Disease Control and Prevention in Atlanta released the latest autism figures on March 30.
CDC researchers used health records, educational records or both to identify children with autism spectrum disorders in parts of 14 states. Data for more than 38,000 kids were consulted.
“Such a big increase in autism spectrum disorders in such a short time seems a little odd, and there’s a lot of noise in these data,” says psychiatrist Fred Volkmar of the Yale Child Study Center in New Haven, Conn.
Some of the clatter stems from divergent diagnostic and record-keeping practices across states and school districts, Volkmar says. Children with various learning problems sometimes get labeled with autism spectrum disorders to receive special education services, he adds.
Rates of autism spectrum disorders fluctuated markedly from one state to another, the CDC reports. Prevalence ranged from 21.2 cases for every 1,000 children in Utah to 4.8 cases for every 1,000 kids in Alabama.
Overall, 1 in 54 boys, versus 1 in 252 girls, had autism spectrum disorders. The magnitude of that sex difference also varied substantially across states.
CDC’s autism data show notable rate hikes among black and Hispanic children, reflecting attempts to correct for underdiagnosis of these conditions in minority populations, says anthropologist R. Richard Grinker of George Washington University in Washington, D.C.
Grinker says the new figures underestimate autism’s U.S. prevalence, because they rely on school and medical record reviews rather than in-person screening. A study he coauthored screened a large population of South Korean children and found that 1 in 38 had autism spectrum disorders (SN: 6/4/11, p. 16).
Psychologist Geraldine Dawson, chief science officer of advocacy group Autism Speaks in New York City, says that her organization is funding a study that will evaluate South Carolina children in person for autism spectrum disorders.