No one knows the direct cause of MS – yet.
There is a widespread belief among doctors and researchers that there is no single cause of MS. Instead, it is believed that MS is the result of a combination of several different factors. A tremendous amount of research is being done to find out what role these different factors play and just how large their effect might be.
Studies are ongoing in the following areas:
MS is generally considered an autoimmune disease. This means that the immune system, which normally protects us from disease and infection, reacts against certain proteins in the body as if they were foreign. In other words, the body mistakenly attacks and harms itself.
In recent years, researchers have identified the role of certain immune cells that trigger MS attacks, as well as some of the factors that cause these cells to do so. They have also noted some sites (or receptors) on the attacking cells that appear to be drawn to the myelin, beginning the destructive process.
Environmental studies suggest that some factor – probably infectious – must be encountered before the age of 15 in order for MS to develop later in life. Several viruses and bacteria have been, or are being, studied to determine if they may trigger MS, but none have been proven to do so yet. The strongest evidence so far points to some involvement of the Epstein-Barr virus (EBV).
Studies have shown that people born in a geographic location with a high incidence of MS, who move to a geographic location with a lower incidence of MS during childhood, will acquire the lesser risk associated with their new location. This suggests that exposure to some environmental factor or factors prior to puberty may predispose a person to develop MS later in life.
Another possible environmental factor is sunlight exposure, as it relates to vitamin D. When exposed to sunlight, your body naturally creates vitamin D, which is known to play a role in immune function and may help protect against MS. Epidemiological studies show more frequent cases of MS in regions that are farther away from the equator, where people have less sunlight exposure and lower levels of vitamin D.
New techniques are being used in an effort to identify the genes that may be involved in MS development. While some autoimmune diseases are caused by one or two malfunctioning genes, MS appears to involve defects in several different genes, each one with only a modest effect.
While MS is not hereditary, having a family history of MS, particularly in a parent or a sibling, does make a person about 2.5 percent more likely to develop MS. In identical twins, if one twin develops MS, the other twin has a 30 percent chance of also developing the disease.
So, while being directly related to someone with MS does raise your risk, it is still a relatively low risk, which strongly suggests that other factors play a larger role in MS development and your genetics are simply a piece of the puzzle.