This thread has been fascinating and I appreciate the time and effort everyone has gone to to explain their point of view.
Can I ask a couple of really basic clarifying questions?
As I understand it, where pain persists and is not structural, then the mind-body approach says that this is a faulty signal in the brain (the "alarm system") and brain retraining can calm things down, as it teaches the brain that the signal is a misfire as the causative issue has resolved. MBCT does similar in that suggests it both reduces pain or at least allows you to cope with it better, ditto depression.
However, this approach seems to have expanded (much like CBT) to other areas, as I understand it, so that any ongoing symptoms after an acute infection or resolved precipitating event are considered to be mind-body/classical conditioning and can be reversed by brain training, as no causative/sustaining event (e.g. viral persistence) has been found.
However, ulcers, which were considered to be stress have now been shown to have a causative agent and this can now be treated with medication, likewise MS.
Listening to Howard Schubiner talk about ME and LC he says that this is the ongoing mind-body, which is classical conditioning, and is creating symptoms long after the acute event.
I know correlation is not causation and this is a really simple question, asked out of genuine curiosity, but doesn't this suggest that we haven't found the right test for the cause yet?
Thank you again to everyone who posted papers and links, I have found it helpful to go back to basics to understand "from the ground up".