Monday, April 19, 2010

Proximity, location, and autism diagnoses: Is there a connection?

April is Autism Awareness month, and if you've been in Boston lately, you've probably seen the posters hanging in T and commuter rail stations -- photos and stories of children with autism, and a question: "What does autism look like?"

To answer the May Institute's question, a person with autism can look like anyone.

Late last year, the Department of Health and Human Services reported that autism was more widespread that previously believed, with about 1 in 100 children on the autism spectrum. The oft-cited link between the MMR vaccine and autism has been officially dismissed, and studies seem to show that now, more than ever, no one knows what really causes or triggers the disorders.

Two new studies by researchers at Columbia University offer new ideas about what causes autism, at least in California, where autism cases handled by the state's department of developmental services increased 636 percent from 1987 to 2003, according to Science Daily. One study points to a cluster near West Hollywood, where children were four times more likely to have autism than babies born in other parts of the state. The other asks whether proximity to a child with autism increases the chances of other children being diagnoses with the disorders.

In the first study, published recently in the Health & Place journal, researchers analyzed data from 11,683 autism cases out of the 4.1 million babies born in California from 1993 to 2001. They identified a 20-kilometer by 50-kilometer "cluster" or area where the autism rate seemed highest, and also noted 38 other "secondary clusters" with high rates. All of the secondary clusters were located in the greater Los Angeles region.

"The identification of robust spatial clusters indicates that autism does not arise from a global treatment and indicates that important drivers of increased autism prevalence are located at the local level," the researchers wrote. While their study did not attempt to pinpoint a single cause for autism, it does suggest that localized environmental toxins could play a part, as well as certain social influences, including "increased awareness of autism, decreased stigma associated with the disorder, or increased number of local advocacy groups," according to Soumya Mazumdar, a postdoctoral research scholar at Columbia’s Institute for Social and Economic Research and Policy who authored the study.

The other study, also by researchers from the Institute for Social and Economic Research and Policy at Columbia University but published in The American Journal of Sociology, shows that children who live near a child who has been diagnosed with autism are more likely to receive an autism diagnosis themselves. How could proximity play a part?

"From shared toxicants, through the diffusion of a virus, as a by-product of neighborhood selection, or through the diffusion of information about autism through social networks," the researchers wrote, adding that "meeting children with autism and having discussions with parents of children with autism could lead parents (of children not diagnosed with autism) to observe behavioral symptoms consistent with autism, to learn how to effectively identify and reach a physician, and to learn how to access and subsequently navigate services and service agencies."

The Columbia University team studied data from more than 300,000 children born in California between 1997 and 2003, and found that children who live within 250 meters of a child with autism have a 42 percent higher chance of being diagnosed with an autism spectrum disorder with the next 12 months. Children who live 250 to 500 meters away have a 22 percent higher chance of being diagnosed, and the greater the distance the less the likelihood of a diagnosis. The "social effect" was more prevalent in cases of mild (or "high functioning") autism diagnoses.

One of our children is on the spectrum (he has Asperger's Syndrome), and I absolutely agree that exposure to a child with autism builds awareness -- perhaps even overawareness -- of the signs of spectrum disorders in other children. It's easy to see how increased awareness could lead to an increase in diagnoses; a generation ago, a child with mild (or "high-functioning" autism would simply have been labeled "difficult" or "quirky," but now we have a better idea of what to look for (and how to help). Also: The autism spectrum itself has grown to include several things, including the all-encompassing PDD-NOS (Pervasive Developmental Disorder Not Otherwise Specified) that would have been dismissed just a decade or so ago.

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