Causes and genetics

Epstein-Barr virus, genes, vitamin D, smoking and weight in adolescence, and how they combine.

Almost everyone with MS has been infected with the Epstein-Barr virus, and the strongest study so far suggests the infection comes first. This lesson sets out the evidence, the leading explanations of how a common virus could lead to MS, and the trials testing what to do about it.

MS is not inherited in a simple way, but genes shape who develops it and, separately, how severe it becomes. This lesson explains what the largest genetic studies have found and what they mean for families.