Environmental
Generally, Multiple Sclerosis has a lower incidence in countries further from the equator. This leads experts to believe that environmental factors also play a role. Studies have suggested the disease to be linked to a reduced exposure to sunlight, or a vitamin D deficit.
Other factors that have been suggested to exacerbate MS include high stress levels, smoking, dietary elements and reaction to some solvents. That said, conclusive proof is lacking for many of the risk factors.