There would be no evidence because there is no official medical treatment to give.
And even off label/experimental treatments (LDN or antivirals if indicated).
Thats my take anyways
ME/CFS is an umbrella term for a multi-system illness with at least ten separate illnesses.
Those illnesses show up in non-ME/CFS patients also, where they have treatment protocols and evidence-based medicine.
Here are some examples:
Autoimmunity: treat the separate autoimmune illness and dysfunction, immune modulators.
Thyroid Subset Illness -- thyroid supplementation
Neuro-inflammation -- treat using anti-neuroinflammatories, especially those with efficacy in other neuro-inflammatory illnesses.
Impaired energy production -- this disorder shows up in non-ME/CFS patients also, treat using protocols that catalyze energy production
Impaired metabolic processes: use existing treatment protocols when those disorders appear in non ME/CFS patients
Muscle aches, pains -- makes sure diagnosis is correct, and then treat: the pain of ME/CFS is very similar to the pain of MCAS, SFN and EDS. FM often misdiagnosed.
Antiviral treatment: Test and measure viral titers. High viral titers need to be treated in any case. ME/CFS patients often have compromised immune systems, which means viruses cannot resolve on their own without sequelae. Recent journal articles showed EBV and HHV 6 begin a cascade of genetic changes that launch ME/CFS immune and metabolic errors.
Cardiovascular, circulatory issues -- established protocols.
Addressing the co-morbidities:
Orthostatic intolerance, vertigo, syncope, POTS, vasovagal issues
Small Fiber Neuopathy, occurs in high percentage of POTS patients
Mast Cell Activation Syndrome: has established treatment protocol based on EBM, ME/CFS is frequently misdiagnosed when illness is MCAS (Klimas)
or MCAS is contributory
Ehlers Danlos Syndrome -- one of the genetic cluster illnesses
Depression, anxiety
Irritable Bowel Syndrome/SIBO -- established protocols.
CSF leak, Chiari, cranial instability -- rule out
This is an extremely complex illness, beyond the practice of a GP.