In Search of the Cause of Autism
How about television?
Autism in the United States has been increasing for two and a half decades, from one child in 10,000 to one in 500 or perhaps even one in 166 today. Maybe advancing parental age is a factor; this Israeli study, published Monday, shows that men over 40 are more likely to father autistic children than men under 30. And it's clear that part of the rise can be attributed to better identification by doctors, improved parental candor, and, especially, an expanded definition of the psychiatric diagnosis for the ailment. But because the autism surge began around the year 1980, researchers and parents of afflicted children continue to ask what kind of exposure could have begun at that time that might account for the surge.
The answer almost certainly isn't mercury compounds in childhood vaccines. What about pollutants, medicines, or vaccine chemicals other than mercury? Or radiation? Or how about this suspect—missing from the usual list of autism malefactors but to which childhood exposure increased significantly in Western countries in about 1980—namely, television.
The idea is wholly speculative. No scientist has shown a link between autism and television, but so far as I could determine no scientist is working on this question, either—and maybe someone should be. Beginning in about 1980, TV watching in early childhood began to rise, coincident with the proliferation of affordable VCRs and cable channels offering nonstop cartoons and kids' shows. The child's brain is self-organizing in the first few years of life, and visual stimuli have much to do with how it organizes. Humans evolved while responding to three-dimensional visual stimuli. The advent of ubiquitous TV for young kids amounts to an unplanned experiment that exposes developing brains to tremendous doses of colorful, moving, two-dimensional visual stimuli. Coincident with this experiment, there has been a sharp rise in the number of children who, through autism, lose their ability to relate to the three-dimensional, normal world.
Television and videos should be investigated as a possible autism agent because no other explanation seems available. Study after study, most importantly this 2004 National Academy of Sciences review, has found no relationship between autism and the mercury-based vaccine preservative thimerosal or the measles-mumps-rubella vaccine in general. The autism increase continued after mercury was eliminated from European vaccines in the early 1990s and from American vaccines by 2001. (Robert F. Kennedy Jr. has argued vehemently that all studies on this point are flawed, but though RFK Jr. is a wonderful person, one doubts he knows more than the entire National Academy of Sciences.) Arthur Allen made the case against vaccines as the cause of autism for Slate last year.
Some of the rise in autism may be caused by ever-lower infant mortality, especially among newborns at risk for illness. For example, babies born with Fragile X syndrome, a chromosome defect related to intellectual disability, increasingly survive infancy and mature into children whose problems include autism. It is possible that the autism increase is also a result of genetic mutation, though the odds are against such a rapid spread of a recessive variation. (Researchers have not yet found a genetic marker that identifies newborns likely to become autistic, leaving unknown whether the condition fundamentally stems from heritable traits or environment.)
Pollutants have been proposed as the explanation, but all forms of pollution except carbon dioxide have been declining in the United States and European Union since the 1970s, and naturally occurring carbon dioxide is much more common than the artificially emitted kind. Toxic pollution has declined by about half during the period of the autism increase. Electromagnetism from cell phones and other devices increasingly zaps through us but at lower levels than the natural radiation to which humanity has been exposed since time immemorial. Kids are getting bigger and that means they have larger brains, but new studies discount brain size as an autism explanation. A flaw of toxicology is the study of chemicals one by one, while our bodies are exposed to many simultaneously; so, it could be that vaccines and other compounds to which young children are now exposed are dangerous in combination. That theory is being considered but so far has not pointed to autism.
Now to television, with the caveat, again, that what follows is speculation. The autism rise syncs closely to the rise in television viewing by the young, especially the arrival of cable channels and affordable VCRs. (I'll use "television" as a stand-in for passive bright-screen-watching.) As recently as the 1970s, cartoons and children's shows were aired only on Saturdays and perhaps a few hours per morning, and there were no movies on cassette. Since about 1980, cartoons and children's shows have become available all day, every day, on TV or through VCRs and now DVD players. Television watching by the very young, rare a generation ago, has since skyrocketed. Shows for infants, such as Teletubbies, have come into being. A recent Kaiser Family Foundation report found that 1-year-old children now average almost an hour per day viewing television and videos, while children ages 2 and 3 watch television and videos an average of about two hours daily.
As young children begin to experience the world, their brains organize partly in response to the stimuli received. Science magazine, the technical publication of the American Association for the Advancement of Science, recently reported several studies showing that "problems in autism result from poor connections among brain areas rather than from defects in a specific brain region." Recent studies have found that when a healthy child is exposed to stimuli, many areas of the brain become active and communicate with each other; in an autistic child, fewer brain areas light up and there is little communication. Studies at the Brain Development Imaging Laboratory of San Diego State University have found that autistic children have a "lack of synchronicity between visual areas in the back of the brain." Of the new research suggesting that defects in brain organization track with autism, Science concluded, "If a neuronal imbalance is to blame, no one knows how it arises." No one does. But the rise in autism disorders during the very period that early-childhood screen-watching has risen is disturbing. Eyes glued to a colorful tube is an intense form of "exposure" for any young child. Correlation does not prove causation, but there's an awful lot of correlation here.
Of course, most children who sit mesmerized by television suffer no harm, other than limited vocabulary and an uncontrollable desire for the latest breakfast cereal. Television viewing may even have benefits. But perhaps while TV is a wash or a good thing for the majority, a small minority of young children are seriously harmed.
Common symptoms of autism include sudden withdrawal from the real world into a world inside the child's mind; transition from love of parents to constant anger against them; engaging in the same actions over and over again, always with an object close nearby. Don't these sound, in a creepy way, like television's unintended effects? Screen-viewing conditions the young mind to withdraw from the real, three-dimensional world of social interaction into a two-dimensional world of internalized fantasy. Parents stop being objects of love and become the child's enemy—after all, they are the ones who turn off the TV! And every parent who has had children with access to a VCR or DVD player and a library of cartoon movies has observed the same phenomena: Young children watch the same movie over and over again.
Gregg Easterbrook is a fellow at the Brookings Institution. His most recent book is The Progress Paradox: How Life Gets Better While People Feel Worse.
Photograph of a boy playing a video game on Slate's home page by Tim Boyle/Getty Images.