Sure, not criticizing positive thinking techniques per se, but pointing out that there is a difference between positive thinking, and the actual objective improvement of symptoms.
Perhaps all of us with ME/CFS could benefit from some psychological techniques that aim to brighten our lives, supply hope, or give us more optimism.
In fact I think this is one of the reasons that ME/CFS patients generally follow all the ME/CFS research very closely, as we are looking for reasons to be hopeful and optimistic.
Myself, whenever I am planning to try a drug or supplement that I read about, and which I think might improve my ME/CFS, even before I start taking it, just doing the research on it puts me in a better, more optimistic mood. 90% of the time it turns out that the drug or supplement I tried had no benefits, and it's then back to the drawing board. But at least for several weeks I was in an optimistic hopeful mood.
POTS often arises after viral infection. Recent studies have found autoantibodies POTS patients which target the nerves of the autonomic nervous system. That seems a plausible mechanism to explain POTS; though the number of studies conducted is small, so this autoimmune research is still in its infancy.
At this point I don't think there is any scientific evidence for DNSR or other psychological therapies helping POTS. Though there are anecdotal stories. However, I imagine that thousands of patients may have tried DNSR, and with that many people, you are bound to get a few that just improve spontaneously.
You find spontaneous resolution in approximately 75% of younger POTS patients. Ref:
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If we get some well-conducted double-blind placebo controlled trials showing DNSR can help POTS, then that might throw a different light on things.