At the same time none of that supports the notion of stress being relevant.
Yes, my guess is that stress was not involved in the ME/CFS outbreaks (it would be hard to imagine how everyone in the villages around Lake Tahoe, or a whole hospital in the case of the Royal Free, all became stressed all together).
But I am trying to construct a bigger picture of how ME/CFS is triggered, and my working theory is a dual-factor theory: the first factor is a virus or other pathogen, which are commonly observed to trigger ME/CFS.
But we know that the viruses linked to ME/CFS are ubiquitous in the population, and do not cause ME/CFS in the general case. Thus logic dictates that other secondary factors must be involved, that only in tandem with the virus lead to ME/CFS.
Those secondary factors might be genetic; but so far genetic studies have not found much in the way of ME/CFS susceptibility genes. So I think an environmental second factor is more likely, and my hypothesis is that the second factor is anything which suppresses the antiviral immune response, which then allows the acute viral infection to run riot in the body. In other words, in my theory of ME/CFS, a virus plus an immune weakening factor puts you at high risk of developing ME/CFS.
I think that in the ME/CFS outbreaks, there must have been a second immune weakening factor present in the outbreak locale which suppresses the antiviral immune response. This would then explain why the virus caused a devastatingly high incidence of ME/CFS in that locale; but when the virus spread beyond that local, it no longer caused ME/CFS (except perhaps for the odd sporadic case here and there).
This is dual-factor theory is the only one I can think of which would explain why the outbreaks always remained localized. If anyone can come up with another theory for the outbreak localization, I am listening. To me this is the only one that makes sense.
In the case of Lake Tahoe, my hunch is that the toxic cyanobacteria growing on the Lake that year suppressed the antiviral immune response.
We also know from Dr Chia's
telling discovery that immunosuppressive corticosteroids, when erroneously prescribed during an acute viral infection, create a high risk ME/CFS. Again, I think this is because the immunosuppression of corticosteroids allows the virus to run riot in the body during the acute infection, giving opportunity for the virus to insinuate itself more deeply into the body.
And this leads us on to why major chronic stress can also act as an immunosuppressive second factor: because chronic stress releases the cortisol hormone, which acts in the same way as corticosteroid drugs to lower the antiviral (but not antibacterial) immune response. Thus I think Chia's corticosteroid discovery supports the chronic stress connection to ME/CFS.
Another factor linked to ME/CFS is organophosphate pesticide exposure, which in one study quadrupled the risk of developing ME/CFS. Again, with organophosphates being immunosuppressive, in my view they can act as the second factor which weakens antiviral immunity.
So this is the bigger picture in which I view the chronic stress connection to ME/CFS. I don't believe in all the psychobabble that the psyches come up with, and I don't believe in the "all in the mind" view of of ME/CFS that the psyches propose. I think chronic stress is just one of many factors which can weaken antiviral immunity, and I think it is this weakening of immunity that allows a viral infection to cause ME/CFS. This has been my working theory of ME/CFS for some years now. I have not found any evidence which contradicts this theory.
I should add that I think it is important to provide a counter theory of the stress connection to ME/CFS, a theory which counters the views of the somatoform psychologists. If we leave it to these psyches, they will invent all sorts of crazy psychobabble reasons as to why stress can cause ME/CFS. But my theory removes all psychobabble, and provides a down-to-Earth biological explanation of how stress can increase the risk of ME/CFS.
I tried to explain my immunosuppressive theory of how stress may cause ME/CFS to Prof Sharpe on Twitter, but as soon as I did, he banned me... I guess he has too much invested in his psychobabble views to consider my biological theory of stress.