One in 68 children in the United States have now been identified with an autism spectrum disorder, according to new Centers for Disease Control and Prevention numbers released Thursday.
The latest estimate is roughly 30 percent higher than the CDC's previous measure, released in 2012, which found that 1 in 88 children had autism, based on health and education records.
According to the new report, among 8-year-olds living in one of 11 CDC surveillance areas across the country in 2010, roughly 14.7 in every 1,000 had autism, though there were some regional differences in rates -- many of them pronounced. In New Jersey, for example, 1 in 45 children had been identified with autism, compared to just 1 in 175 in Alabama.
Overall, the new report mirrors earlier estimates, finding that autism is roughly five times more common in boys than in girls. One in 42 boys were affected, compared to just 1 in 189 girls. White children were more likely to be identified with autism than black or Hispanic children.
The global prevalence of autism has increased twenty- to thirtyfold since the first population studies were conducted in Europe in the late 1960s and '70s, according to background information provided in the new report. At that time, research suggested that only 1 in 2,500 children in Europe were affected by autism.
The CDC began tracking autism rates in the U.S. in 2000 with the establishment of its Autism and Developmental Disabilities Monitoring Network, which relies on health and education records. Early estimates found that autism affected roughly 1 in every 150 children -- a number that has steadily increased with each subsequent report. (A separate 2013 CDC report estimated that 1 in every 50 children in the U.S. have an autism spectrum disorder, or ASD, although that was based on parental reports, not official records.)
It's still not precisely known what is causing the steady rise in autism diagnosis.
"There has certainly been an increase in awareness, and that drives families toward earlier action ... It drives them to ask questions at earlier ages, and it also increases the probability of detection," Rob Ring, chief science officer with the nonprofit Autism Speaks, told The Huffington Post. "We also know that surveillance itself is improving. Groups like the American Academy of Pediatrics have instituted guidelines for screening, which increase the chances of picking up kids who have been missed previously."
Ring added that the diagnostic criteria for autism has changed over the years, most recently with the release of DSM-5 -- the so-called "bible" of modern psychiatry. Among other things, the new edition of the DSM has folded Asperger's syndrome into the broader category of ASD.
"But that's not the full picture," said Ring. "We know that risk factors such as increasing parental age are likely adding modestly to increases as well. Science continues to reveal interesting interactions between genetics and the environment."
Autism is a spectrum disorder, meaning there is a wide range in the ways and degrees to which it affects people. Its cause is unknown, though it is generally thought to be a combination of genetic and non-genetic factors.
Notably, the new report found that most children tend to be diagnosed after age 4, despite advances that have made it possible for diagnosis to happen as early as age 2. That figure suggests that too many children are "missing out on the transformative benefits on outcomes that early intervention offers," Ring said. "Earlier diagnosis has got to be a priority."
In a statement, Coleen Boyle, director of the CDC's National Center on Birth Defects and Developmental Disabilities, echoed the sentiment.
"Community leaders, health professionals, educators and childcare providers should use these data to ensure children with ASD are identified as early as possible and connected to the services they need," she said.