There has always been a strong feeling that something environmentally is behind the ever increasing diagnoses of autism in children.
Like ADD/ADHD, autism is a genetic disorder but that doesn't explain why estimates of as many as one in 150 children in certain parts of the U.S. have some form of autism. Researchers are not sure why this disorder has actually become more prevalent.
Historically, from the 1940s to 1960s, mothers were blamed for a lack of affection shown toward their autistic children. More recently, the mercury-based preservative in measles vaccinations were thought to be a cause of increased autism. Today, researchers who recognize that heredity plays a central role in autism are also looking into the possibility of interaction with environmental factors, both in the womb and after birth.
Anna Baumgaertel, a developmental-behavioral pediatrician at the Children's Hospital of Philadelphia, says some of her autistic patients have been heavy video and TV watchers since birth--a factor she thinks, "may lead to autistic behavior in susceptible children, because it interferes with the development of 'live' auditory, visual, and social experience."
Professor Michael Waldman of Cornell University, a recognized expert in the field of applied microeconomics, doesn't pretend to be an authority on autism. He became engrossed in the subject in the fall of 2003, when his 2-year-old son, David, was identified as having an autism-spectrum disorder. Hoping to eliminate any potential triggers, Prof. Waldman supplemented the recommended therapy with a sharp reduction in television watching. His son had started watching more TV in the summer before the diagnosis, after a baby sister was born.
Prof. Waldman says his son improved within six months and today has fully recovered--a surprising result, given that autism is typically a lifetime affliction. "When I saw the rapid progress, which was certainly not what anyone had been predicting, I became very curious as to whether television watching might have played a role in the onset of the disorder," he says.
Prof. Waldman and his colleagues approached autism and TV by putting together weather data and government time-use studies. They found that children tended to spend more time in front of the television when it rained or snowed. Precipitation became the group's instrumental variable, because it randomly selected some children to watch more TV than others.
The researchers looked at detailed precipitation and autism data from Washington, Oregon and California---states where rain and snowfall tend to vary a lot. They found that children who grew up during periods of unusually high precipitation proved more likely to be diagnosed with autism. A second instrument for TV-watching, the percentage of households that subscribe to cable, produced a similar result. Prof. Waldman's group concluded that TV-watching could be a cause of autism.
To those who wonder about the autistic children who never watched TV or who had clear problems before they started watching, Professor Waldman responds that his hypothesis isn't meant to be all-inclusive. "Even if we are correct, there are likely other triggers and possibly some children become autistic even in the absence of any trigger," he says.
Harvard economist Jeffrey Miron has started a project to test Prof. Waldman's methods and results. Prof. Waldman welcomes the scrutiny, saying he hopes his work will also provoke autism researchers to conduct clinical trials. "Obviously this is an unusual thing for an economist to be looking at," says Prof. Waldman. "Maybe I was overconfident. We'll see."
Source: The Wall Street Journal, February 27, 2007