Opinion Conversations on the science of autism research.

Rising rates

by  /  30 March 2012

About 1 in 88 children in the U.S. has an autism spectrum disorder (ASD), according to a new report from the Centers for Disease Control and Prevention (CDC). That’s a 23 percent increase over rates the federal agency reported in 2009.

The data come from a nationwide network, the Autism and Developmental Disabilities Monitoring (ADDM) Network, which tracks the number of 8-year-old children with ASDs in 14 different communities throughout the country.

According to the ADDM, prevalence increased from about 1 in 150 children in 2007 to 1 in 110 children in 2009 to 1 in 88 today. That’s a nearly 80 percent increase from 2002 to 2008. The data are based on children who were 8 years old in 2002, 2006 and 2008, respectively.

The CDC report also shows that rates vary widely across the different sites, from 1 in 47 in Utah to 1 in 210 in Alabama. New Jersey (prevalence rates shown at left), for example, has consistently higher rates than the national average. Researchers who led the New Jersey component of the study say they believe this is because of well-informed healthcare providers in the area and early identification.

However, it is still unclear how much of the increase is due to increased awareness of autism and to changes in the way the disorder is diagnosed. Though the standard diagnostic criteria have remained broadly the same since 1994, when they were published in the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV), the way clinicians interpret them can change.

A study published in 2009 found that a more than 600 percent increase in autism diagnoses in California between 1987 and 2003 was due to “social and demographic changes, such as more children born to parents over 40, more active neighborhood networks, and evolving definitions of the disorder….”

Changes to the diagnostic criteria for autism accounted for about 25 percent of the increase, and younger age of diagnosis accounted for another 25 percent.

In 2010, the same research team found that children living in close proximity to a child with autism had a 40 percent greater chance of being diagnosed with autism themselves, suggesting awareness may play a major role in driving up prevalence rates.

The new analysis also finds that more children are being diagnosed at a younger age — 3 years — though most are still diagnosed after 4 years of age; Asperger syndrome typically isn’t diagnosed until 6 years of age.

The largest increases in prevalence rates occurred in Hispanic and black children, likely because of improved screening and awareness in these communities.

Though the CDC report shows increased prevalence across intellectual abilities, the greatest increase occurred in children with autism who have average intelligence. More than 60 percent of the children in the study identified as having the disorder did not have intellectual disability.

Looking ahead, changes to the diagnostic criteria — due out in 2013 when the DSM-5 is published — may again change prevalence rates, though how much is not yet clear. Some studies have suggested the changes will make it more difficult for people with normal IQ scores to get an autism diagnosis.

The new findings again highlight how important it is to figure out the factors behind the rise in autism: Whether it truly can be attributed to better awareness among doctors and families or whether there is some environmental or other factor contributing to an actual rise in the disorder are questions the autism research community must try to answer.

2 responses to “Rising rates”

  1. RAJensen says:

    The CDC just published their latest autism prevelance rates in the US now 1 in 88. That was predicted by Allen Francis, the editor of DSM-IV (1994) who has stated that the field trials of DSM-IV failed to predict the false epidemics of autism, attentional disorders and bi-polar disorder.

    Plomins group in the UK has tested thousands of twin pairs recruited from the Twins Early Development Study (TEDS)registry and found that 10% of all general population children have what they called severe autistic traits. Milder autistic-like traits would penetrate even deeper in to the general population.

    Cox et al (2005)reported that that 26% of women and 19% of men described themselves as ‘very shy’ when they were growing up. That result is even higher than the Plomin groups finding that 10% of general population children possess severe autistic traits.

    The rubber band keeps stretching until it will break. That’s what DSM5 is designed to do, make an autism diagnosis much more restrictive,what Volkmar, who opposes the DSM5 proposal, has called ‘stopping the epidemic in its tracks’. Under current concepts of autism as being dimensional it is not unreasonable to suggest that the eventual autism prevelance rates may fall as low as 1/5.

    In DSM-IV the diagnostic criteria for the severest sub-category, Autistic Disorder, consists of sixteen isolated symptoms none of which is specific to autism suggesting that even in severe cases diagnostic criteria is ambigous and subjective at best.


  2. Anonymous says:

    Cox et al (2005) in a large study of nearly 6,000 particpants found that social phobia is common in the general population and 26% of women and 19% of men in the study describe themselves as being ‘very shy’ when growing up.

    Stein et al (2001) found that people with generalized social phobia had a first degree relative who scored higher on measures of trait anxiety and social anxiety and concluded that social anxiety was familial in part.

    In the baby sibs studies in the US researchers have reported that the younger sibs of autistic children who were recruited when the mother was pregnant had high rates of autism at 18 to 24 months of age. Many of the affected baby sibs lost their dagnosis withen a year or two.

    Perfectly consistent with familial social phobia. Given the massive broadening of the concept of autism and based on the Cox study we could easily be headed towards an eventual prevelance rate of 1/5.

    It should also be noted that the prevelance of the severest sub-category Autisitc Disorder hasn’t changed much over time about 0.2%.

    Psychiatrists who specialize in autism may be living in a bubble. They see the unaffected parents and siblings but fail to recognize just how common the ‘broader autism phenotype’ extends into the general popuilation.



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