Does Autism Spread Through Word of Mouth?

Autism and Network Effects

Posted Apr 09, 2010

Some of the skyrocketing increase in autism diagnoses in the United States has to do with sociological forces — people talking to one another about the disorder, sharing information about doctors and providing friends and colleagues with information about educational resources. The research does not imply that autism is “made-up,”  but rather that as information spreads more widely about the disorder, cases of autism get “discovered” that might not have been discovered earlier. Much of this sociologically-driven increase is for cases of autism on the mild side of the autism spectrum.

Researchers at Columbia University say that a child who lives 250 meters from another child who has been diagnosed with autism has a 42 percent increased chance of being diagnosed himself or herself. Children who live between 250 and 500 meters of another child diagnosed with autism have a 22 percent increased chance of being diagnosed themselves. The researchers based this conclusion on a study of more than 300,000 children in California between 1997 and 2003. Children who live further away from another child diagnosed with autism have a lower risk of being diagnosed themselves.

Researchers Peter Bearman, Ka-Yuet Liu and Marissa King found that the disorder spread in the same channels through which information spread — social connections were the key here. Children living in the same school district as a diagnosed child, for example, were more likely to be diagnosed than children merely living proximally to a neighbor’s child with autism. Children exposed to similar environmental conditions but who shared different social networks were less likely to experience the shared diagnosis effect.

Basically, what the study — published in the American Journal of Sociology — suggests is that for clear-cut cases of severe autism, parents seek out help from doctors and educators without needing much input from friends and members of their social network. But in milder cases, the influnce of those social networks can be decisive. Autism cases have surged nationwide in recent years, often by several hundred percent. The new study does not contradict earlier work that has explored various environmental and genetic risk factors for autism, but adds another piece of the puzzle to explain the sudden surge in cases.

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