Kristie McNealy, MD

Yesterday, while I was hopping around the net, reading posts from other people who are blogging for Autism Awareness Month, I came across a post from OneMom, who outlined some of the details and background information behind the CDC study that resulted in the much publicized 1 in 150 figure for autism prevalence, a number which received a lot of press back in February 2007 because it was touted as the highest rate of autism ever found in the US.

When first heard that number in a radio news blurb, I’ve wondered where it came from, and what it really meant. The announcer had read “autism,” but clearly, he couldn’t really be talking about classical autism. In 4 years of medical school, concentrating on a career in pediatrics, and doing rotations in the child development clinic (where the team which diagnoses autism works), and in various clinics which saw special needs kids at a major children’s hospital, I had only seen one child with classic autism, and one kid who was somewhere on “the spectrum.” I had seen many kids come in to see the child development team because of fears of autism, and all but one left with other diagnoses (language disorders, dyspraxia, normal children with paranoid overly cautious preschool teachers. . .).

Of course, more reading on the net at the time, revealed the fact that the 1 in 150 figure referred to all autism spectrum disorders (ASDs). I’m not sure why I never sought out the actual study myself, but when I found it yesterday, this is the part that caught my attention (emphasis mine):

Because participating sites were selected through a competitive federal award process and not specifically to be representative of the entire U.S. population, ADDM Network results cannot be used as a basis for estimating the national prevalence of ASDs. Two national surveys designed as random samples of the U.S. noninstitutionalized population estimated prevalence of ASDs from parental reports of autism diagnosis among children aged 6–8 years to be 7.5 and 7.6 cases per 1,000 population, respectively.

So, from what you can see, this study was never designed to be able to give a generalizable population estimate. It was designed as a surveillance system, using sites that were not randomly selected. The individual populations studied in this report had widely differing autism prevalences, from a low of 1 in 303 cases in Alabama and as many as 1 in 94 in New Jersey. In addition, there own report references two prior studies which both found a prevalence of autism that was higher than 1 in 150 (7.5 in 1000 equals roughly 1 in 133).

In the end, I don’t think we really know much about the actual prevalence of autism. Regardless of the numbers, the fact remains that autism (and ASDs) has an enormous impact on the children and families who receive this diagnosis. It is a difficult diagnosis to cope with, and the therapy is expensive and time consuming. Autistic children and their families cope with many daily struggles, and they deserve to have their legitimate treatment covered by insurance and other programs. They do not need the resources available to treat autism diluted by a plethora of children who are diagnosed just because autism is trendy.

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