In basic terms, scientists simply don’t know what causes multiple sclerosis, or MS. Your genes – the genetic material that you inherit from your biological parents – play at least some part. But they are not the sole cause.
In MS, your immune system goes haywire and starts to damage your central nervous system (brain and spinal cord). Scientists are still trying to figure out how this response works and what causes it. Scientists think that for some people, genes may cause your immune system to interact with something in some way to cause the disease.
These may include:
Environment. Environmental factors, like smoking, low levels of vitamin D, and obesity in childhood, have been shown to raise the risk for MS. People who live in certain parts of the world – for instance, those further away from the equator – tend to get MS more often. The reasons for this aren’t yet clear. Some scientists think it involves higher vitamin D levels near the equator.
There are also some theories that exposure to things like chemical solvents and allergens, among other things, contribute to MS risk. But research hasn’t shown this yet.
Infections. Infection with certain germs may raise your risk for MS. Research points in particular to the virus that causes mononucleosis (Epstein-Barr virus). But scientists are also investigating measles, human herpesvirus-6, and others.
Who Gets MS?
One of the reasons scientists assume a role for genes in the development of MS is that some closely related groups get the disease more than others.
To start with, women are twice as likely as men to develop MS. It’s also more commonly diagnosed in white Americans than Black Americans or those of Asian heritage. And MS is rare or doesn’t exist in many Native American societies. This all suggests that genes may also play a role in who gets MS.
In addition, though many groups share some of the same genes or gene mutations that raise MS risk, this is not always the case. For example, in one study, of 73 genes that raised MS risk in white Americans, only eight did the same in Black Americans. Are there other genes that raise the risk of this disease for Black Americans but not for white Americans? What are they, and might they change the approach to treatment?
More research needs to be done on the causes of MS, both in general and in different ethnic groups so that we can understand both the risk factors for MS and the right way to treat it in different people.
Can You Inherit MS From Your Parents?
Not really. There is no known gene or set of genes that guarantees that you will get MS if your parents have it. But a family history of MS does raise your risk for the disease.
For example, the rate of MS in the general population is about 1 in 1,000. But if you have a parent with MS, your chances go up to 1 in 50. And if both parents have MS, your risk goes up further to about 1 in 8. Other possible family history situations show that the closer your relationship to someone with MS, the higher your chances of having it:
- If a second-degree relative (grandparents, uncles, aunts) or third-degree relative (great grandparents, great uncles and aunts, first cousins) have MS, your risk is about 1 in 100.
- If your sibling or non-identical twin has MS, your risk is about 1 in 20.
- If your identical twin has MS, your risk is about 1 in 4.
Scientists are especially interested in statistics about twins because identical twins have exactly the same genetic material. So if genes were the sole cause, both should have MS. But most of the time only one twin gets it, which means other things are at work.
Which Genes Raise Your Risk for MS?
Scientists know of more than 200 genes or genetic variations (mutations) that may contribute to MS. A lot of these genes help build and maintain the immune system. Some of them are linked to other diseases that also involve a malfunction of the immune system, such as Crohn’s disease and rheumatoid arthritis.
Others simply increase your chances for developing certain risk factors for MS. For example, lower vitamin D levels raise the risk of MS in some people. Certain gene variations are linked to lower vitamin D levels and thus a higher risk of MS. And genes that raise your risk of having high BMI (a measure of body fat) – another risk factor for MS – also make you more likely to get the disease.
In some cases, there may be particular gene mutations that raise your risk of MS, but in many people, it seems to be that no single gene raises your MS risk, but that it’s the interaction of several of them.
Researchers continue to look for more clues about the relationship between genes and MS.