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What causes multiple sclerosis?

Multiple sclerosis symptoms are caused by damage to the nerve fibres that send messages to and from the brain.

MS is an autoimmune disease, and the nerve damage happens when the body attacks the protecting coating around the nerves called myelin.

Doctors still don't understand why the body turns on itself in this way causing MS, but several theories are being studied. Rather than there being a single cause, a mixture of genetic and environmental factors are thought to play a role in MS.

Multiple sclerosis is not infectious or contagious.

Sunlight and vitamin D

MS is more common in countries further away from the equator, such as the UK, where there's less sunlight.

Summer sunlight enables the body to make vitamin D in the skin. There's some evidence linking lower levels of vitamin D and MS, but vitamin D supplements haven’t yet been proven to help reduce the risk of developing MS.

Genetics and MS

MS is not thought to be directly inherited. No single gene has been proven to cause MS.

However, research suggests there is an increased risk of developing MS if a close blood relative has the condition.

Viruses and MS

Some research has suggested that viruses such as measles, herpes, Epstein-Barr virus and the flu viruses may be associated with MS.

Theories suggest a virus may stay dormant for some years, but wakes up again at times, causing MS attacks.

These theories have not been proven.

Blood flow and MS (CCSVI)

Researchers have been investigating whether narrowed veins near the brain, reduced blood flow and a build-up of iron deposits inside nerve tissue could trigger MS and its symptoms.

This is known as cerebrospinal venous insufficiency or CCSVI. Studies have also looked at whether widening any narrowing of the veins using a technique called angioplasty would help MS symptoms.

So far the evidence is that CCSVI treatment doesn't improve a patient's health and in some cases may make symptoms worse.


There is some evidence that smoking increases a person's risk of developing MS. Although this theory needs further research, it is possible that chemicals in cigarette smoke affect the immune system.

WebMD Medical Reference

Medically Reviewed by Dr Sheena Meredith on July 25, 2016

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