A series of data sets analysed in a paper by economists at Cornell University and Indiana University-Purdue University suggest a connection between early childhood television viewing and the onset of autism. The authors urge further investigation and research by experts in the field.

In a paper which was presented in October 2006 at a conference of the National Bureau of Economic Research in Cambridge, Mass, the authors reviewed data from the Bureau of Labor Statistics American Time Use Survey on TV viewership rates among children and compared it with data from the National Climactic Data Center, which looks at the amount of precipitation communities receive. This analysis showed that children from rainy counties watch more television. When autism rates were then compared between rainy and drier counties, the relationship between high precipitation and levels of autism was positive.

‘We tested our hypothesis using existing, well-known data,’ said Michael Waldman, a professor of economics at Cornell's Johnson Graduate School of Management and a co-author of the research paper. ‘The analysis shows that early childhood television viewing could be an environmental trigger for the onset of autism and strongly points to the need for more research by experts in the field of autism.’

Thirty years ago, it was estimated that roughly one in 2,500 children had autism, while today some estimate that number to have increased more than tenfold, to as high as one in 166. At the same time, television viewing has increased dramatically due to easy access to cable and satellite television, more traditional broadcast offerings and the market penetration of VCRs and DVDs.

Because there are no large data sets that track whether children who watch a lot of TV when they are young are more likely to develop autism, the authors examined the connection between autism and two factors that generally increase the amount of TV that young children watch: precipitation and access to cable TV.

They found that current school-aged children who live in California, Oregon, and Washington, counties that received large amounts of rain and snow when the children were young, are more likely to be diagnosed with autism. Furthermore, children who grew up in California and Pennsylvania counties during the 1970s and 80s with high cable subscription rates were also more likely to be diagnosed with autism.

These analyses control for differences between counties in income, population, and demographic mix - other factors that may influence the autism rate - and also examine changes in county autism rates over time as well as differences at a point in time.

‘Our analysis is not definitive, but it certainly raises questions that seem to have gone unasked in autism research to date,’ added Sean Nicholson, an associate professor of policy analysis and management in Cornell's College of Human Ecology.

‘The medical community is increasingly convinced that something is happening in the environment that triggers an underlying biological or genetic predisposition toward autism, and these findings strongly support the need for taking a closer look at early childhood television viewing.’

Waldman and Nicholson were joined by Nodir Adilov, a professor of economics at Indiana University-Purdue University, in their research.

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Click here for more research reports on possible causes of autism

First Published in April 2007

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