I wonder to what extent holding scientifically accepted beliefs about free-will alters ones experience of this phenomenon. I could understand how it might be terrifying to people with judeo-christian beliefs, but what about someone who is already a secular neuroscientist? I wonder how many people may be experiencing this without being perturbed or feeling the need to seek medical help.

Also, it isn't clear to me whether people with this condition are "missing" something, or if they are in some way perceiving their thought processes with greater fidelity than the rest of us. People have plenty of biological features that aren't necessary for survival (male nipples, tailbones, etc), could the illusion of free will be similar?