I used to laugh at people feigning back problems because there was no physical evidence of disability, until one day I stood up at my computer and down I went.
I don't think everybody with these maladies is a hypochondriac, but I suspect many are. If you think you're sick, you're sorta are. Speaking of back problems, I had two pairs of vertebrae fused about 4 years ago. I still have a lot of pain and numbness issues, but it would be worse if I had not had the surgery.