YI wouldn't call them a susceptible person either. Addiction I could understand, but dealing with something like IBS did quite surprise me...
Hypnotherapy is a deep state of relaxation and yes, it does work.

It's just a case of altering your state of mind, of course it works but you have to let it. It's a way of embedding thoughts into your brain so when you see something that memory will be triggered which may help you decide to change your course of action thus rendering the therapy a success.