Cancer is more fatal, yes. But cancer diagnosis/treatment/prognosis are well established by the mainstream medicine and they are well accepted by patients. That doesn't leave much to imagination unless the patient is, well, neurotic. The situation with CFS is totally different. Nothing is well established or accepted, and therefore it's only natural to imagine on your own about the cause, treatment and prognosis. It's a human instinct. And it's made worse because CFS patients feel they've been neglected and abused by the main stream medicine. The problem is that such imagination can lead you do things that doesn't help, or reject things that may help. Hence I think CBT could be useful for some CFS patients by dispelling imagination and start managing the disease with the best available info.