Since Drs Klimas and Fletcher were involved in this, I'd almost guarantee the CFS/ME cohort was a good one -- probably patients from the Klimas/Rey patient group.
When I was at their office last week, Dr K stopped in the midst of her busy day to chat for a few minutes with patients in the waiting room. (What an amazing woman she is!) She mentioned that GWI patients and ME patients look very similar -- same symptoms -- but have different abnormal lab results.
It appears that that GWI patients were poisoned by organophosphate pesticides imbedded in their uniforms. These "safe" uniforms were not safety tested under the conditions in which they were often used -- in extreme heat and inside chem safety suits.
There is also some question of indirect sarin (also an organophospate agent) exposure when one of Saddam's chemical weapons depots was blown up upwind of troops. So, GWI patients appear to be chemically poisoned by some form of nerve agent. There may also, of course, be contributing genetic or other factors.