I have narcolepsy myself. I don't think it has hindered my training at all, although I think jiu-jitsu definitely helps my narcolepsy. It is the best investment in my health - physically, psychologically, and spiritually - that I have ever made.
I once rolled with Nick Newell, the one-armed MMA fighter with a 10-0 record. While trying to pass my guard Nick used his nub, which was extremely hard, and he apologized because he felt it was advantage. I told him not to worry about it because I intended to use both of my arms, which I felt was a bigger advantage. He eventually heel-hooked me. Fortunately, it only sprained my ankle. Nick felt horrible but I told him that I deserved it because I underestimated him because of his disability - I didn't think he could finish it with one arm and a nub so I let it go too far.