There was a very interesting article in the Wall Street Journal (February 2, 2010) on the rise of autism. The WSJ discusses two newly released research studies that further the discussion about “location” as a major indicator of autism. For example, why is a child born in northwest Los Angeles four times more likely to be diagnosed with autism as a child born elsewhere in California? Medical experts have pondered for years why autism rates have soared nationwide, and why the disorder appears to be much more prevalent in certain communities than in others. Now, some recent studies about areas in California, may shed some light on these baffling questions.
Researchers from Columbia University, in a study published in the current Journal of Health & Place, identified an area including West Hollywood, Beverly Hills and some less posh neighborhoods that accounted for 3% of the state’s new cases of autism every year from 1993 to 2001, even though it had only 1% of the population.
Another recent study, from the University of California, Davis, published in Autism Research, also found high rates of autism in children born around Los Angeles, as well as nine other California locations. Autism, usually diagnosed before a child is 3 years old, is a developmental disorder characterized by impaired social interaction and communication and repetitive behavior.
Both of the California-based studies suggest that local environmental or social factors are driving the high autism-diagnosis rates. And they conclude that childhood vaccinations—which some people fear is a factor behind rising autism—are not to blame. Otherwise, diagnoses of the disorder would be more evenly dispersed, they say.
The studies also disagree on some points. According to the UC Davis study, greater concentrations of autism occur in communities where parents are highly educated, which could mean they have more awareness of autism and access to treatment. By contrast, the Columbia researchers discount the role of educational levels. They believe that social influences, such as shared information about diagnoses, doctors and services, are largely responsible for the high rates they found in parts of Los Angeles.
Some of the increase in autism rates in past decades is due to changing definitions. Until the early 1990s, diagnoses of autism were rare and included only children with low I.Q.s, who were deeply withdrawn and had very minimal language skills. In 1994, diagnosticians adopted the term autism spectrum disorder (ASD), which also includes children with impaired social skills but not necessarily severe intellectual disabilities or language delays.
On average, one in 110 American 8-year-olds had an autism spectrum disorder in 2006, an increase of 57% since 2002, according to a December report from the Centers for Disease Control and Prevention. Some parts of the U.S. are seeing much higher rates than others: Metropolitan Phoenix, for example, has twice the prevalence as northern Alabama. Whether those differences reflect actual higher risk in different regions, differences in awareness among local residents, or simply variations in record keeping is something the CDC is trying to untangle.
“We still don’t know what causes autism, and we don’t know a lot of the underlying factors, so we can’t rule out the possibility that there are differences in the distribution of risk factors.” says Jon Bai, a CDC epidemiologist. Theories abound to explain the steep increase that has occurred in recent years. Some experts attribute it to genetic changes within families. But others say genetic changes wouldn’t occur so quickly and instead they blame environmental toxins or childhood vaccinations.
Another possible explanation: Greater awareness of the disorder, and programs in some parts of the country that can help children regain skills, may make parents more willing to have their children diagnosed. “But awareness can only go so far” to explain the rising levels of autism, says Dr. Baio. “We are still identifying more children with autism, in all levels of severity, than ever before, which is why this continues to be a perplexing and urgent concern.”