What role does environment play with ms?

Unclear: Lots of interest currently in the interplay of genetic background of a population and environmental triggers. No one clear winner here, but studies of large populations are seeing some patterns emerge with regard to annual sunshine exposure, vitamin d (and its receptor), epstein barr virus (mononucleosis) infection at a critical time in life, possibly smoking as contributing to risk for ms.

MS: It plays a role but it is difficult to say exactly what percent of interaction it has with ms considering that multiple sclerosis is an autoimmune disease. Environment plays a role in all diseases but how much it plays is almost impossible to decipher.

Excellent question: MS will not occur in absence of environmental triggers. These include cigarette smoking, low vitamin D levels, adolescent obesity, latitudes north of 39-42 degrees, presence or absence of GI parasites, prior Ebstein-Barr infections, maybe prior herpes zoster, to name the best accepted.