I think that brain retraining could result (however briefly) in an increased sense of personal control over the illness. Perhaps dopamine is released or endorphins or some other neurotransmitters.
It may also include a bit of magical thinking and placebo response.
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If one employs relaxation techniques, learns to tolerate some of the milder intrusive symptoms somehow (I am not convinced that moderate to severe symptoms can be downplayed by the mind's efforts) this concerted effort by a PwME or FM may release more beneficial neurotransmitters and thereby improve mood. But a better mood doesn't make one more adept at preventing relapses or PEM episodes; in fact, a better mood might engender more activity and less carefulness, more PEM, more relapse, more severe symptoms.
And I want to mention that the Bateman Center is located in Salt Lake City, Utah, and the leadership and many local clients could be subject to more easily have magical beliefs relating to healthcare, due to their religion. I haven't studied the link, if any; it is conjecture on my part.
Pleasing clients by validating their scientifically unevidenced therapies----would that increase the amount of donations? Or is it a move in be "inclusive" to all patient views..