New Evidence: TV viewing causes Autism

I like to keep an eye out for new research on Autism or Asperger's Syndrome, ever since reading this article in Wired. Today Slate reports on a study showing a strong correlation between cable-TV households and Autism rates.

The Cornell study looks at county-by-county growth in cable television access and autism rates in California and Pennsylvania from 1972 to 1989. The researchers find an overall rise in both cable-TV access and autism, but autism diagnoses rose more rapidly in counties where a high percentage of households received cable than in counties with a low percentage of cable-TV homes. Waldman and Nicholson employ statistical controls to factor out the possibility that the two patterns were simply unrelated events happening simultaneously. (For instance, petroleum use also rose during the period but is unrelated to autism.) Waldman and Nicholson conclude that "roughly 17 percent of the growth in autism in California and Pennsylvania during the 1970s and 1980s was due to the growth in cable television."

Autism occurs frequently (at least, more frequently) among children of high-IQ parents, and autism rates have been exploding in tech-heavy cities, including Seattle. In an almost amusing part of the study, rain is an incidental factor:

But the fact that rising household access to cable television seems to associate with rising autism does not reveal anything about how viewing hours might link to the disorder. The Cornell team searched for some independent measure of increased television viewing. In recent years, leading behavioral economists such as Caroline Hoxby and Steven Leavitt have used weather or geography to test assumptions about behavior. Bureau of Labor Statistics studies have found that when it rains or snows, television viewing by young children rises. So Waldman studied precipitation records for California, Oregon, and Washington state, which, because of climate and geography, experience big swings in precipitation levels both year-by-year and county-by-county. He found what appears to be a dramatic relationship between television viewing and autism onset. In counties or years when rain and snow were unusually high, and hence it is assumed children spent a lot of time watching television, autism rates shot up; in places or years of low precipitation, autism rates were low. Waldman and Nicholson conclude that "just under 40 percent of autism diagnoses in the three states studied is the result of television watching." Thus the study has two separate findings: that having cable television in the home increased autism rates in California and Pennsylvania somewhat, and that more hours of actually watching television increased autism in California, Oregon, and Washington by a lot.

This study shows correlation, not causation (a caveat I ignored in the title of this post as dramatic license) but does have a good recommendation:

If television viewing by toddlers is a factor in autism, the parents of afflicted children should not reproach themselves, as there was no warning of this risk. Now there is: The American Academy of Pediatrics currently recommends against any TV for children under the age of 2. Waldman thinks that until more is known about what triggers autism, families with children under the age of 3 should get them away from the television and keep them away.