Multiple sclerosis (MS) is a disease in which the immune system mistakenly attacks the myelin sheath (a fatty protective coating) that covers nerve fibers and foster communication between the brain and the body. The loss of the myelin sheath leads to nerve cell degeneration, and a range of disease symptoms.

The exact cause of MS is not known, although researchers believe multiple factors contribute to the development of the disease.

Immune factors

MS is considered an auto-immune disease. But it is not known what causes the immune system to mistakenly attack the myelin sheath, and myelin-producing cells called oligodendrocytes, to disrupt the transmission of nerve impulses. Research is ongoing into factors that activate or influence the workings of immune cells throughout the central nervous system.

Environmental factors

A number of environmental factors may contribute to a person’s likelihood of developing MS, including:


MS is more prevalent in some geographical regions than others, with a highest disease prevalence found in countries of northern Europe, and throughout the northern U.S., southern Canada, New Zealand and southern Australia. The distance a person lives from the equator seems to correlate with a risk of developing MS, with more patients identified in regions that are farther from the equator.

Vitamin D

Vitamin D is important for immune system health, and there appears to be a link between vitamin D deficiency and a person’s chances of developing MS. This deficiency could also explain differences in disease prevalence by geographic location, since people living closer to the equator are more exposed to sunlight year-round so their bodies produce more vitamin D.


Smoking is linked to an increased risk of developing MS, and evidence suggests that patients who are current or former smokers can develop more rapidly progressing forms of the disease.


Obesity is thought to contribute to MS because it promotes chronic low-grade inflammation, which can affect immune responses.


Some infections have been linked to MS, with the Epstein-Barr virus that causes mononucleosis getting significant attention in recent years. A number of research findings indicate that previous infection with Epstein-Barr can contribute to the risk of MS.

Genetic factors

MS is not a heritable disease, and does not run in families. However, genetic factors may predispose people to the disease alone or in combination with environmental or infection risks.  Some 200 genes are thought to possibly contribute — even in small ways — to MS development.

A variant, or mutation, in a gene involved in the immune system, called HLA-DRB1, is now thought to be the strongest genetic risk factor for this disease.


Multiple Sclerosis News Today is strictly a news and information website about the disease. It does not provide medical advice, diagnosis, or treatment. This content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this website.