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Every once in a while I run across a paper that I have no idea what to make of. That happened earlier today, when I read a paper titled “Does television cause autism?” by Waldman, Nicholson, and Adilov (you can read the entire paper at that link). Television causes autism? If you’d asked me this morning, I’d have told you that was crazy talk, but this as of yet unpublished (and unsubmitted, apparently, which means unreviewed) paper takes the idea very seriously. Well, they don’t really set out to show that television is the cause of autism, but that it’s part of a causal chain that begins with genetic predispositions toward autism spectrum disorders. One of the explanations for the increase in the incidence of autism spectrum disorders over the last few decades is that the genetic predisposition requires some sort of environmental trigger, and that the prevalence of this trigger has increased during the period that has seen an increased incidence of autism. Waldeman et al. hypothesize that television is that trigger.
Why do they pick television? They list four reasons, which, when taken together, suggest television as a candidate for the environmental trigger. The reasons include the fact that television viewing has increased among children over the last few decades (due largely to increased access to cable television), the connection between television watching and ADHD, and behaviors consistent with television watching among “at risk” infants. That’s only three, right? I saved the last for a sentence of its own, because once again, it’s just odd: autism rates are extremely low among the Amish, who don’t watch any TV at all (you have to have electricity to watch TV).
As if things weren’t already surreal by this point, the first study is just odd. They start by using the Bureau of Labor Statistics’ American Time Use Survey to show that the amount of television households watch, on average, is positively correlated with the amount of precipitation an area gets. When it rains, people watch more TV. They then show that autism prevalence is positively correlated with the amount of precipitation an area gets. This indirectly associates television watching and autism. To strengthen their case, they also show in a second study that in two states (California and Pennsylvania), the prevalence of autism in a county during the 70s and 80s is positively correlated with the percentage of households in that county that have cable.
So that’s the evidence. It’s not just correlational, it doesn’t actually involve correlating autism and television watching, but autism and something that is correlated with television watching, and autism and cable — not watching cable, but owning it. Like I said at the beginning of the post, I have no idea what to make of this. I suppose it’s definitely enough to foster future research on the question, but before anyone starts fearing that their infant’s TV watching habits might cause him or her to develop autism, keep in mind that this study is pretty convoluted. I don’t like to use the old “correlation is not causation” objection because, well, in the absence of alternative explanations, correlation is often really good evidence of causation. But in this case, we don’t actually have a correlation between autism and television viewing rates, so we’re left with all sorts of potential third (fourth, fifth, sixth… nth) variables. Hell, maybe precipitation causes autism. Why not?
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