White has written against the idea that there is one Functional Somatic Syndrome: Here's a debate with Simon Wessely: I think it may be a bit of a misuse of the term "heterogeneous" in medicine if one recommends the same treatment to everyone. One will have people of different weights/BMIs for most conditions for example but one wouldn't say they were heterogeneous. The GET manuals e.g. in the PACE trial are the same for everyone. He doesn't want for example different programs for ME compared to other groups.