Dwight Meredith over at PLA pointed out to me that the UC-Davis study on the prevalence of autism in California is online. It hasn't been published in a journal yet, and the JAMA paper I mentioned last week doesn't reference it. But the editorial comment in the same issue does.

As it should, since there's certainly an issue to be resolved. The Davis authors feel that their evidence makes it more likely that autism is actually increasing, even after correcting for wider diagnostic criteria, and so on. They still couldn't correct for all the potential differences in case finding, though, and it's unknown how much this has affected the final numbers. The JAMA editorial points out a recent paper analyzing the same California data which concluded that "diagnostic substitution" had occurred - a decrease in the "mental retardation" category had been taken up by an increase in the autism category.

Dwight's view, I believe, is that there has indeed been a real increase in autism - although short of the epidemic that some in the press have spoken of. I look forward to seeing how more data prove or disprove this - if there really is an increase, it's a tragedy, of course, but it could also provide a rare chance to uncover some important facts about the etiology of the condition. You don't get many good shots at the causes of a complex syndrome like this.

I think that's one reason the thimerosal provision that worked its way into the Homeland Security bill upsets me. Unlike many, I don't see it as evidence of a conspiracy to cover up wrongdoing (although one of the worst parts is that it provides spectacular ammunition to those who do.) I think that the less political maneuvering and grandstanding there is on this topic, the better. Most things would be improved that way, come to think of it. I did a quick Google search while writing this post, and since it had "autism" as a search term, up popped a sponsored link on the right-hand side of the page: "Child vaccines are linked to autism. Free case review by our lawyers." I'm glad these guys are so certain.

It's going to be hard enough to figure all this out without all the bricks flying through the air. As I've said, I think that thimerosal is a red herring. But if autism really is on the increase - and I'm still on the fence about that - then finding the real cause would be the most important research priority in the whole field.