Firstly, psychosomatic means physical symptoms due to psychological cause, so if there was no physical thing happening inside the body, it wouldn't be psychosom

Firstly, psychosomatic means physical symptoms due to psychological cause, so if there was no physical thing happening inside the body, it wouldn't be psychosomatic. (It would just be psychological). There are many types of stress, e.g. physical (exercise), viral, or psychological, and they all have a similar effect in the brain (i.e. all of those stresses activate the HPA axis). From what I can see, the type of shutdown due to chronic stress that we see in CFS and similar conditions is likely due to the central governor[1] or Boksem's cost-benefit analysis centre[2] (which may actually be the same brain areas) deliberately generating fatigue due to excessive negative stress. So the mechanism isn't "lack of sleep causing damage, resulting in fatigue", it is more along the lines of "central governor sees that we aren't getting enough sleep, and then deliberately generates fatigue to tell us we need to sleep more". So even though it's not a psychological primary cause, it's probably fair to say that the fatigue is psychosomatic because the brain is doing a psychological determination based on a physical input. (The same would apply for excessive exercise resulting in overtraining). If you prefer, you could call it "functional" rather than psychosomatic. I prefer not to get caught up on terminology, and instead concentrate on what's actually happening in the body. [1] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3323922/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3323922/ [2] https://www.researchgate.net/publication/51426280_Mental_fatigue_Costs_and_benefits https://www.researchgate.net/publication/51426280_Mental_fat...