Autism is much more common than previously thought, according to a new government report that estimates that 1 in 68 children have some form of the disorder.
Boosting the rate has become a two-year ritual since the
As in the past, researchers could not say what was driving the increase. While the role of environmental factors remains an open question, rising awareness of the disorder, greater detection and improved access to services have all been shown to be significant factors in the explosive growth in diagnosis over the last two decades.
To arrive at an estimate, CDC researchers do not examine any children directly. Instead, they comb through health and education records for hundreds of thousands of 8-year-olds, looking for indications of autism — either a formal diagnosis or symptoms of the disorder.
The analysis released Thursday was based on data collected in 2010 from 11 surveillance areas around the country, including ones in Maryland, Wisconsin, Arizona and Colorado. People living in the surveillance areas represent 9% of the U.S. population.
Research has long shown that boys are most susceptible to autism, and, indeed, their rate — 1 in 42 — was far higher than the rate in girls — 1 in 189.
But large geographic and racial differences in the rates illustrate the difficulty of relying on records to determine the true prevalence of the disorder.
Alabama had the lowest rate — 1 in 175. The highest rate was in New Jersey — 1 in 45.
The rate for whites was 1 in 63, which was 30% higher than for black children and 50% higher than for Latino children.
There is little evidence to suggest that such differences have anything to do with biology. Rather, they probably reflect differences in the degree to which the diagnosis and services have taken hold in different communities. In some places, doctors and school officials are more likely to make a diagnosis or take note of symptoms and include them in records.
The CDC analysis found that much of the racial variation stemmed from a high rate of diagnosis among white children of normal or above-normal intelligence.
Historically, the vast majority of people with autism were thought to be mentally retarded. Today, that is no longer the case — especially among whites. The CDC found that only 25% of those identified as autistic had an intellectual disability. That figure was 48% for black children and 38% for Latinos.