@Avenger you are quite right.I have experienced it myself and it is so annoying and unscientific I sometimes felt I was in the Twilight Zone.As far as I know every "Syndrome" seen as an expression of Somatization Disorder have later been proven to be a real disease.I've seen an article arguing that the existence of Somatization Disorder is not proven at all, with the criteria of the scientific method.I've looked it up again and couldn't find it but to be fair there are so many cases of Somatization Disorder that I can't imagine it not exist.
It's a very different thing though to have one or 2 symptoms that is your personal manifestation of this disorder (even "blindness" has been documented as such a manifestation) than having a specific set of symptoms, often affecting different systems, that precisely match the symptoms of many many other people.
As far as this goes, it doesn't sound wrong, depending on what they meant exactly.
It's even in one of the citations you posted.If gut flora and brain can affect each other in both directions, it's not crazy if an early psychological trauma caused a microbiome change that set a perpetual cycle that can be very hard to resolve by itself.
I agree that gut flora and brain can affect each other; but so can so many other environmental factors (antibiotics can select for bacterial overgrowth alone; fluoride, chlorine, antibacterials, chemicals and some medications including proton pump inhibitors can affect the microbiome and more recently Covid-19 Virus has been found to alter the microbiome). My own belief is that causation is likely to be multifactorial. I just mistrust the Psychologists who have repeatedly taken ownership in the belief that they can stop ME/CFS purely through Cognitive Behavioral Therapy; which the article had concluded. I also agree that long term stress can have very negative effects upon all organs including the brain; and even students have been found to be at higher risk of developing colds and infections during the period of intense study.
But I see the drive from Psychology has so far been to bend the truth and take control (Pace Trials) to save money at our expense now to possibly include Long Covid. I greatly doubt that ME/CFS causation is solely the product psychological trauma and ME/CFS according to the ME Association is often found associated with Viral outbreaks or epidemics and many with ME have cited Glandular Fever and Viral infections (myself included).
I agree that a period of stress can also affect your immune system and could contribute towards any illness including ME/CFS and could well be a contributing factor or one of a number of possible factors; but....
I am basing much of this on my own experience due Psychiatrists mislabeling D-Lactic symptoms as Somatization for 18 years; because the Psychiatrists did not understand that the multiple symptoms could relate to any organic causation; and after only one short twenty minute appointment diagnosed the symptoms due to anxiety and Somatic, when I showed no anxiety even during severe symptoms, which long term caused me more stress on top of being unwell ; Then more recently finding that most of the Gastroenterologist's that I have met have little understanding of D-Lactic acidosis and no Doctors have had any understanding Bacterial Overgrowth. So there is a huge gap in training and understanding; so how can Psychiatrists make such statements with authority if they were never trained to understand the complexity or the Microbiome which may still take decades or longer to fully decode or the relationship with policing immune system or Gut/brain axis? I see the change in the microbiome towards Bacterial Overgrowth and D-Lactic acidosis in terms of an infection; and with so many negative environmental factors there seems to be more evidence of organic causation.
I have no trust in Psychiatrists and the NHS are still tying to label me with 'Chronic Fatigue Syndrome' which has been put on my discharge summary recently on two occasions and I have been told that '' D-lactic acidosis is not on the list, as it is very rare, so the doctor has selected ‘Chronic Fatigue Syndrome’ as that is the nearest option they have for abnormal fatigue''. Even though I have a diagnosis and I am prescribed cyclical antibiotics as treatment, they do not want to acknowledge D-Lactic acidosis. The system could not have tried harder to break me over the past 20 years.