I've seen several of these studies, and they generally find that
amalgam sufferers report more somatization (higher scores on the
Symptom Checklist 90 R) than the controls. Unfortunately, I don't know
what the individual items on the SC-90-R look like. I would guess that
they go something like "I go to the doctor for treatment for symptoms,
but the doctor says there's nothing wrong with me". A person that would
endorse such an item would be
assessed as somatizing. PLEASE NOTE: the author of the SC-90-R,
DeRogatis, did not write the scale with Hg poisoning in mind, but it is
often used to assess amalgam sufferers.

Another aspect of these studies (of which yours appears to be a typical
example) is that the researchers screen subjects for their "amalgam
sufferer" and "control" groups so that they are matched on the number
of amalgam surfaces, age, sex, etc. The only difference is that the
"sufferer" group has physical complaints which they ascribe to the Hg,
while the control group does not. By definition, this must lead to the
conclusion that the Hg cannot be responsible for any of the physical
complaints.
Carolyn