The thing about neurofeedback is that it is a way to balance brain wave patterns. "MCS" per se is not identified or labeled in any way. The person doing the treatment is merely looking at the brainwave pattern presented. Anything seen out of balance is identified as out of balance (too high, too low, etc) and treated by bringing the brainwaves slowly back to a more balanced state.
There are some medical doctors doing neurofeedback. It is not a "psychological treatment" per se. One opthamologist uses it for people who are nearsighted to correct their vision.
The issue here is that a more balanced brain will allow the body to be working at its optimal level. Thus the immune system will be strong and the likelihood of getting other illnesses is lessened. Or if the person does contract something their immune system is strong and they are able to recover much faster and more easily than someone with a weakened immune system.
Accidents certainly can happen to damage the body regardless of your mental status. The issue becomes whether or not the initial damage moves into a more general problem associated with more and more exposures (as in mcs) or if it just ends with that one incident.