TV Might Cause Autism

Slate reports:

The Cornell study is by Waldman, a professor in the school's Johnson Graduate School of Management, Sean Nicholson, an associate professor in the school's department of policy analysis, and research assistant Nodir Adilov. "Several years ago I began wondering if it was a coincidence that the rise in autism rates and the explosion of television viewing began about the same time," Waldman said. "I asked around and found that medical researchers were not working on this, so accepted that I should research it myself." 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."

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 Levitt* 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.

You'll want to read this whole piece.