The exact cause of multiple sclerosis isn't known. A person's genetics may be involved, as well as the environment he or she lived in early in life. Some scientists believe that a virus or other factors may even be involved. Let's take a closer look at each of these possibilities.
The likelihood for developing multiple sclerosis may be inherited, meaning passed on from parents to children. We know that relatives of people with MS are at increased risk of developing the disease.
It's currently believed that several genes can make a person more likely to get multiple sclerosis. Some researchers feel that MS develops because a person is genetically more likely to react to something in the environment. Then, when he or she comes in contact with that agent, it triggers the immune system to attack the central nervous system.
The environment itself is also thought to play a role in the development of multiple sclerosis. The rate of MS varies widely between different groups of people.
For example, MS is especially common in Scotland, Scandinavia, and northern Europe.
In the United States, MS occurs more frequently in whites than in other racial groups.
People from Africa or Japan rarely get MS, but African Americans and Japanese Americans do.
Research shows that MS is more common in certain parts of the world. For example, the number of cases of MS increases as you get farther from the equator. If you move from a high-risk area to one with lower risk, you take on the risk of your new environment. However, this only happens if you move there before your teenage years. So, it's possible that being exposed to a certain agent in the environment before puberty may make a person more likely to get MS.
Also there have been "epidemics" of multiple sclerosis, where many people in the same area develop the disease. This also suggests a potential link to the environment.
Finally, some doctors and scientists believe that different viruses can trigger multiple sclerosis, but this has yet to be proven. MS is not contagious, but it's possible that a germ almost everyone has come in contact with may cause an abnormal reaction in the immune system. This would only happen in people who are already at risk of developing MS.
Now, there are a few other factors that might play a role in MS. There is growing evidence that hormones can influence the immune system. Sex hormones, such as estrogen and progesterone in women and testosterone in men, may limit the activity of the immune system.
The levels of estrogen and progesterone are very high during pregnancy, which may explain why pregnant women with MS usually have fewer symptoms. The higher levels of testosterone in men may partially explain why there are more women with MS than men.
To better understand this disease, researchers continue to study all the potential causes of multiple sclerosis.