While the exact cause of MS is unknown, researchers have identified a number of factors that increase susceptibility: Geographic location: People who spend the first 15 years in countries located far from the equator are more likely to develop MS. Family history: The lifetime risk of MS in first-degree relatives of people with MS is 2-4%, which is approximately 7-10 times higher than the risk of the general population. Genetic makeup: Researchers have identified more than 230 genes that each increase the risk of developing MS. Most of these genes are known to play a role in immune responses, which supports the view that MS is an autoimmune disease. Race: While MS can occur in people of any race, people of western European ancestry are more likely to develop the disease. Sex: Relapsing-remitting MS is 2-3 times as common in women as in men. Viral infection: First-time exposure to Epstein-Barr virus, which causes mononucleosis, as an adult may increase the risk of developing MS. Lifestyle: Lifestyle factors like cigarette smoking and absorbing insufficient amounts of vitamin D are associated with higher chances of developing MS or a more severe course once developed.