My husband has been taking LDN for several years now. As he has SP his symptoms have been getting worse and he concluded he might as well stop taking it but he did not mention it to me at the time. Within a few weeks he had really gone downhill it was only as we were discussing what might have changed that he mentioned the LDN. I suggested restarting it, which he did. After a few months he is back on a more even keel.
It does seem that for him it is not a miracle cure but it certainly seems to be keeping the symptoms, fatigue etc. down and is giving him some quality of life. It is not perfect, but in general things do seem to be better with rather than without LDN would be our conclusion.
Of course it could all be coincidence, but who knows unless they carry out some research.