Is multiple sclerosis preventable?

No: Since we don't know the cause, it would be unlikely. It is thought to come about from genetic causes, possibly environment and possibly an insult to the immune system.

Maybe, rarely: We do know that people who grow up north of latitude 39 may have higher incidence of ms, but if they move south before the age of 13 or 14, the risk drops to the level of the new environment. In this way, maybe a lower chance of an environmental influence, but how does one really know?

No: Population studies have suggest that mononucleosis in adolescence, smoking, and possibly childhood obesity are risks for developing ms. However ms is a complex variable disease requiring genetic predisposition along with some environmental trigger(s), possibly influenced by hormones, immune system priming from certain infectious agents.