Researchers have found particular kinds of nerve damage in veterans who report Gulf War illness.

This does not tell us anything about what caused the illness, or by what mechanism. All human thoughts, knowledge, and tendencies have a biological basis in the brain, so it is not inconceivable that this damage results from certain thoughts or experiences. However, brain damage usually results from trauma or exposure to certain chemicals.

Either way, we now see that the veterans have a real illness; the Pentagon should stop accusing them of malingering or imagining things.