Hi Ar, Yes, they found a link between CFS and O.H., through many researches conducted. If you search on google using; "CFS and Orthostatic Hypotension" and "CFS and Orthostatic Intolerance", both of those sets of search words will take you to MANY sites. You probably already know it is also called "Neurally Mediated Hypotension"(NMH). This term helps better to describe the fact that it is a neurological problem. The involuntary nervous system is affected by an abnormality of sometimes unknown cause. This involuntary (also called autonomic) nervous system, regulates the things in our body we don't control (BP, Heart Rate, Kidney Function etc...).
Sometimes they use a "tilt-table test" to diagnose it, which tests your blood pressure when upright and at sudden changes from horizontal to verticle positions. I know for a fact mine would be abnormal! As I've said before, it is also a form of "Dysautonomia" (abnorms in nervouse system).
You will find that the articles on that search will talk about NMH and the tilt table test etc...
I once told one of my past Docs, "I have orthostatic intolerance/hypotension, real bad" and all he said was that he knew a basketball player once, that if he got off the bench too quick to play in a game, he would drop to the floor because of orthostatic intolerance, "he damn near broke his nose". This was THE ONLY response I got. No suggestions of any kind! I then said "isn't O.H. a form of dysautonomia?" He replied "what's that?".
Since then I've not spoken to any other Docs about it, not being in the mood to be patronized and ridiculed.