Is there actually any statistical evidence for increased prevalence of ME/CFS? We still don't have an official lab test for it, so we can't have reliable figures for how many people have it. There's certainly been a rise in the number of people who believe they fit the criteria. Earlier, people were diagnosed as 'lazy' or 'malingering' or having a variety of illnesses that couldn't be proven true or false.
I'm not claiming that the incidence hasn't increased; just that we lack the tools and historical data to answer the question.
There are other people better fit to answer that than me. I haven't studied the literature enough to know whether there is either flimsy or sound evidence of the increase in incidence. Anyone who has an opinion on this, please chime in.
When it comes to the of understanding "syndromes" like ME/CFS and fibromyalgia, we have lumpers and splitters. I am a lumper, and think there is a common thread between them. That if we'd have a perfect understanding of one, we would have a clear understanding of the other. Perhaps it's the same mechanisms, perhaps not. But if we widen the net a bit, and see that many autoimmune illness have increased in incidece (have they? I haven't studied it) then that would be at least an indication that it's also the case for ME/CFS, if there is a lack of studies proving ME/CFS increased in incidence.
It would also be useful to know whether IBS has increased in incideces, since X % of IBS patients also have ME/CFS, and some 50 % av ME/CFS patients also has IBS. It would be just circumstansial evidence, but better than nothing.
Anyways, what I can say is that I know several doctors personally, who is now either just retired or will retire soon, and what they say is that it's their impression after a long life as doctors that there are many more now than before who come with the type of symptoms we call ME/CFS. This is of course not sound evidence, so chime in anyone who has a perspective on this.
I think it would be useful for the ME/CFS community if we would build a set of questions a hypothesis of ME/CFS must answer. A set of questions anyone who has a hypothesis of ME/CFS, either their name is Wessely or Lipkin, Jane or John Doe, agree that their ME/CFS hypothesis must seek to answer.
If we assume ME/CFS is just some sort of stress reaction, that would mesh with the gender ratio of PTSD. But the PEM is a complete mystery if ME/CFS is just a PTSD like illness, as virtually all studies on PTSD show that exercise is a great PTSD medicine which gives relief.
Without going into detail, using the mast cell / histamine hypothesis we could think of PEM somewhat like patients with asthma who deteriorate after exercise.
(EDIT: If I had more time, I would have written a shorter post)