More than once I have raised the idea that the placebo effect has been documented as very strong in people with MS. The strong prevalence of placebo effect is one of the reasons that the red flag gets raised on all these treatments, diets and even surgical procedures that have not been proven through rigid controlled studies but still have many people sure that it will be beneficial because of the anecdotal evidence.
There is an article in the spring issue of Momentum, the official NMSS, that talks specifically to this idea and how to harness it to benefit us. The disease modifying drug trial participants who were given placebos had a 15-40% decline in the frequency of attack.
the nocebo effect comes when you know about possible negtive side effects and then experience them yourself, even though you have been give a placebo.
http://nationalmssociety.org/multimedia-library/momentum-magazine/momentum-spring-2011/index.aspx
You will find the article under the green tab marked "healthy living."
best, Lulu