I've been afflicted with what seems to be CFS for at least 10 years.
I've been through the exasperating process of seeking diagnosis and treatment from conventional doctors.
In the absence of any answers, I had to take matters into my own hands and attempt to get well with non-conventional remedies like paleo dieting, detoxing, nutritional supplements, yoga, etc.
Nothing really moved the needle in any sustained way until I started experimenting with emotional healing therapies that work to identify and release deeply-held subconscious traumas and self-sabotaging beliefs.
I've been doing that for 5-6 years now, and my wellbeing keeps improving at an ever-increasing rate.
So, my n=1 anecdata suggests that yes it's a physiological ailment (i.e., involves mitochondria, ATP, cortisol, inflammation, oxidation, T-cells, and many other material processes within the body), but that stress and trauma is a major factor, and that by addressing the stress/trauma component, the physiological component corrects itself, slowly but surely.
There is plenty of evidence to give credence to this explanation, if you simply search for studies linking excessive cortisol (a stress/fear/anxiety hormone) to immune function, auto-immunity and inflammation.
What seems to be lacking in the mainstream medical zeitgeist is an acceptance that stress/trauma can be held deeply in the subconscious, and that there are effective techniques to identify and resolve it.
But I can attest, yes, anecdotally, that it is a real phenomenon, and that effective treatments exist. If this were to be included in the research, I'm confident that CFS can be understood and an effective remedy can be made available to all sufferers.
Any researchers who are interested to know more about my experiences are welcome to contact me (email in profile). I have some lab pathology reports on things like cortisol levels, iron/zinc/copper (and other minerals), thyroid hormones, inflammatory and auto-immunity indicators, chronic infection antibodies (EBV, CMV). I'd be very willing/happy to get other tests, as I'm not yet fully healed, so there's still time to do before/after comparisons of relevant indicators.