They are very common both in the general population and in patients in health care, and may develop into chronic impairing conditions such as somatoform disorders
Absolutely insane that modern medicine not only believes in stuff as random and arbitrary as the modern equivalent of the humors, but has so thoroughly lost the ability to judge reality about this issue that they can see nothing wrong with the suggestion that something on the order of a quarter of the population might suffer from this. This is an extraordinary claim whose entire evidence is speculation about things that "may" be relevant of "can" happen and nothing else. Extraordinary claims with zero evidence. That's religion, or at least it's belief.
That's the line of reasoning that goes from a quarter to a third of all medical appointments having no explanation to baseless claims such as this, calling this speculative ideological construct "very common". Even though the very best that can be said about any single claim in here is: you can't prove it's wrong, a well-known logical fallacy that really strikes home how disastrous things are, falsification being one of the most important principles in science. The only reason why medicine is credible is that it's supposed to be based on science. This is throwing away the only thing that makes medicine credible.
Even more so that there can be regular publication of articles boasting about developments, which never actually show any development. All they do is describe what they did and thought recently, which is nearly identical no matter how far back it goes, the only differences is how it's explained. There is nothing there, there are decades of publications in the past on the same basis, it's an ideology that is both older than a century and perpetually new.
Let's be clear about one thing, and I do not mean this to be negative about them, but this here is a social science. It is not based on hard science, it is people talking about people with other people based on no coherent process or logical structure. There are branches of philosophy that are almost hard science compared to this.
Pseudoscience is now on equal footing with actual science in medicine and is now very common. This is a sad fact. Even worse is that it's on equal footing exactly where it matters the most: where healthcare meets patients. Often in a process that takes all but 2 minutes to come to an opinion that has no basis in reality, with the speculative pseudoscience actually overruling proper science.
Even the field of economics has largely accepted that supply-side economics, giving money to rich people so that it will "trickle down" on the rest of us, is a scam. This is as if the field had made it the only acceptable economic theory. Beyond absurd.