What causes MS?

In Depth: Symptoms of MS Meditation vs. MS 10 Tips to Beat Insomnia Diagnosis: 4 Types of MS What Causes MS?

"What's different here is that we now know that it is the major effect - that is, no other genes have an effect as large on causing MS," she tells WebMD.

Pericak-Vance says no one knows exactly what causes MS, but it is thought to be a complex interaction of genetic and environmental factors.

What Causes MS?

Some scientists think that one unknown pathogen (a small thing that causes illness) may cause MS in people who already have a high risk of getting the disease.

Some viruses can cause myelin damage, and there are some viruses that have been shown to make people more likely to get MS. Even though scientists and doctors have many ideas about things that could cause MS, no one has found a cause that explains every case of the disease.

To learn more about what causes MS, see What Causes MS?

While the genes do not cause MS, they make people more likely to develop MS when exposed to certain environmental factors or viruses, experts say.