Nothing stirs debate quite like the proposition that exposure of young children to mercury might explain the rise of autism and related disorders in recent years.
A while back the Institute of Medicine concluded that the mercury-containing vaccine preservative thimerosal couldn't be blamed for autism. Some advocates rejected that finding and have pressed for further investigation.
So we offer, for your consideration, a pretty thorough set of mercury measurements in hundreds of preschoolers that showed no difference between the kids with autism and the kids who were judged to be normal. The findings were just published online by the journal Environmental Health Perspectives.
The work was done by researchers at the UC Davis MIND Institute, who are running a long-term study looking at genetic and environmental risks for autism.
This sort of science is complicated, and the researchers took pains to control for all sorts of factors, such as fish consumption, that could tilt the results. In the final analysis, they concluded that children with autism and autism spectrum disorders had levels of mercury that were very similar to those in normal kids.
Of course, they note the measurements were taken after an autism diagnosis in affected kids and at the same ages in the control group of normal preschoolers. So if really early exposure to a bunch of mercury in the blood is the problem, they wouldn't necessarily have seen that.
In a statement on the work, lead scientist Irva Hertz-Picciotto said:
Just as autism is complex, with great variation in severity and presentation, it is highly likely that its causes will be found to be equally complex. It's time to abandon the idea that a single 'smoking gun' will emerge to explain why so many children are developing autism. The evidence to date suggests that, without taking account of both genetic susceptibility and environmental factors, the story will remain incomplete. Few studies, however, are taking this kind of multi-faceted approach.