Mercury and Yeast
A summary of a rather good study on mercury as a possible factor is provided here:
http://www.autism-watch.org/rsch/journals.shtml
Here is a snippet:
“This study is strong evidence against the notion that mercury toxicity causes autism.”
There may well turn out to be an interaction between genetic and environmental factors in ASDs. For instance, some scientists believe that an element in the environment might, at least in some cases, trigger a genetic predisposition. However, most studies cast substantial doubt on mercury or yeast as likely variables.