Does Television Cause Autism?

One of my favorite activities in grad school is attending the weekly departmental seminar. During the fall and spring semesters we invite scholars from various universities to give talks on health services and health economics projects they happen to be working on. You can check out current and past seminar schedules here.

This week's presenter discussed some interesting research looking at whether exposure to television at an early age serves as a trigger for autism. If that sounds provocative to you, you're onto something: this paper was probably one of the most talked about studies in 2007. Go ahead and google "television" and "autism" and you'll see.

The basic idea of the paper is to use county-level measures of autism rates and early life (i.e., prior to the age of 3) television watching over a period of several years and to explore the correlation. The authors note this correlation need not imply causation: autistic children (or those with a predisposition to the condition) may be attracted to TV or TV and autism may be correlated with a third, unobserved factor. To get around this, the authors use random variation in precipitation (it rains, kids go inside and watch TV) and the differential diffusion rates of cable TV (cable makes TV more attractive since there are more channels for kids) also at the county-level as instruments to exploit "random variation" in TV watching. A good summary of the study can be found in this Slate article. I highly recommend it.

You might be skeptical and, if so, you are not alone. A lot of people don't buy the results. I personally think its an interesting study. The authors are careful not push the results too far and only suggest that their estimates should motivate future research in the area. Their empirical methodology is as rigorous as it can be given the data. I think most people who have actually read the paper will agree with me, unconditional on whether they ultimately buy the link or not.

Unfortunately, this paper has caused quite a firestorm among autism advocacy groups and medical professionals. Indeed, the results and suggested causal mechanism made many people very angry. I'm assuming the parents in advocacy groups are upset because the finding somehow implicates them as "bad parents." Some public comments accuse the authors of not understanding autism at all. Somebody should tell them that the first author's son is autistic.

More troublesome, though, is the way some (not all!) medical professionals have reacted to the study. This is interesting to me given that nobody knows what environmental triggers may push a predisposed kid towards autism (obviously, I am making an assumption about the underlying biological model here) and that medical researchers are pursuing equally kooky theories like the mercury-in-vaccine/autism link seriously. Given the current state of thought, doesn't it make sense to take the findings of a carefully done study seriously, at the very least to generate further research?

It all makes me wonder whether the vociferous naysayers have actually read the paper and made an honest attempt to judge it on its scientific merits.

(Aside: Perhaps in fairness to the naysayers, I should note this research is somewhat atypical for an economics paper. The television-autism hypothesis is not huge theory in medicine and it certainly has not generated a huge literature anywhere. As implied earlier, the role of this paper is to empirically generate a hypothesis for further testing rather than actually testing some existing theory. Given all that, I can see how some would see this finding as coming out of "left-field." That being said, a lot of the "armchair epidemiology" studies I blogged about earlier fulfill this role as well, and the medical community dutifully notes and (usually) tests the generate hypothesis in another sample or with better data. Why can't we treat this study the same way? Especially when it is methodologically superior to the vast majority of the "armchair" nonsense.)