What causes MS?
The answer still remains obscure. Many studies suggest that both genetic and environmental influences play important interacting roles in determining risk for developing MS. MS prevalence varies with geographic location such that MS is more common in high northern or southern latitude regions and less common in equatorial regions. This peculiar finding is perhaps due in part to emigration patterns of higher risk groups, but most recently have been suggested to be related to less sun exposure and abnormalities in vitamin D metabolism more prominent at higher latitudes.
Various infectious causes have also been considered over the last 60 years, although none have shown a clear association with the disease. Recently, attention has been re-focused on the Epstein-Barr virus as a possibly important influence early in life, but there is no evidence that MS is infectious. Neither is MS is an inherited illness in any classic sense, but genes do appear to play some role in determining susceptibility to acquiring MS.