I will share with you some of what I have discovered about this topic;
I belong to a study group of people from across the spectrum of life styles, backgrounds, etc- all of us have Fibro. Some have only fibro, some are combo patients with other medical problems. The common pattern that we see is that; people with more severe backgrounds have it more severe, those with less of a stress background have lighter/easier symptoms. The tiredness seems to be the same across the board. In our study, the patients with the highest level of pain, pain related complications etc are those from a sexual abuse background, PTSD, depression, then from physical/mental/verbal abusive situations; military people-people from bad marriages-high anxiety people, high stress people either from job or home life, , personality, then third seems to be people that have always "burned the candle at both ends" and then had a traumatic event happen-car accident, surgery, major injury etc type of sudden onset of trauma or has medium to moderate stress over a long period of time.
The major common issue we all have; INSOMNIA and over 60% of us have Vit D deficiency.
So did our "stress" cause us to have insomnia- then from the insomnia and not getting good recuperative sleep trigger our bodies? Did hi levels of Cortisol over the long period of time cause damage to our nervous system? I think it is a combo of things that after a certain point- our bodies 'broke' in a complex way.