The chance increases in families where a first-degree relative has the disease.Thus, a brother, sister, parent, or child of a person with multiple sclerosis stands a one-percent to three percent chance of developing multiple sclerosis.
The general population has less than a one-percent chance of developing multiple sclerosis.These statistics suggest that genetic factors play a major role in multiple sclerosis.However, other data suggest that environmental factors also play an important role.
Although its role is unclear, genetics may play a role in multiple sclerosis.Similarly, an identical twin runs a nearly 30% chance of acquiring multiple sclerosis whereas a non-identical twin has only a 4% chance if the other twin has the disease.
European gypsies, Eskimos and African Bantu essentially do not develop multiple sclerosis, while Native Indians of North and South America, Japanese and other Asian groups have a low incidence.