In this article researcher S. Jill James implicates low glutathione and heavy metal exposure in autism. This may be the case, but glutathione has a number of important functions that have nothing to do with heavy metal binding. As an antioxidant, glutathione reduces toxic free radicals. Glutathione is also a key factor in the maintenance of cellular redox poise. It goes without saying that it is also possible that low glutathione is correlated with, but not causative of, autism.

Todd P. SilversteinWilliamette University
Salem, Ore.

I would venture that at least part of the explanation for the rise in autism’s incidence is related to its recent recognition. When I was a kid, there was no such thing as autism. You can’t diagnose something you don’t recognize.

Andrew Nelson
Santa Barbara, Calif.

Studies published in the past 2 years have investigated the extent to which autism’s increasing incidence traces to changes in diagnosis. At least a few of these studies have found that incidence has increased even after accounting for better diagnosis. —J. Raloff