MS Definition

Multiple Sclerosis: What Factors Cause MS?

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Multiple sclerosis is an immune-mediated disease. In these types of diseases, the body’s immune system attacks its own organs and tissues.

Some experts believe MS is an autoimmune disease. (The prefix ‘auto’ identifies that the immune system is reacting to an antigen that is created naturally within the body. To date, no specific antigen has been identified as the cause for this immune system attack, which is why some multiple sclerosis-specialists are hesitant to use this label.)

The primary purpose of your immune system is to help fight the foreign invasion of harmful substances or organisms in the body. For example, your immune system is designed to fight off infections that are caused by viruses or bacteria.

Generally, the immune system uses inflammation to protect itself and fight foreign substances in the body. However, with multiple sclerosis, the inflammation produced by the immune system is misdirected against parts of the central nervous system.

The cause of multiple sclerosis is not yet clear. Three factors may cause for variability among people. They are:

  1. environmental changes
  2. infections
  3. genetics

Potential cause of MS: Environment

Researchers have noticed an increased pattern in cases of multiple sclerosis in countries that are located the furthest from the equator. Sun exposure is one way for the body to get vitamin D. The correlation between decreased sun exposure and increased levels of MS has led some to believe that a vitamin D deficiency may play a causal role in multiple sclerosis. 

Vitamin D is extremely beneficial for your immune system. People who are closer to the equator are naturally exposed to more sunlight and as a result, their bodies may be able to produce more vitamin D.

Research published in the journal Neurology in October 2017 seems to confirm this correlation. The study used serum samples from over 800,000 women in the Finnish Maternity cohort. Using an an adjusted conditional logistic regression, the researchers found that an increase in vitamin D [25(OH)D — also known as calcifediol or 25-hydroxyvitamin D] of 50 nmol/L was associated with a 39% reduced risk of multiple sclerosis.

The researchers concluded: “These results directly support vitamin D deficiency as a risk factor for MS.”


Other environmental factors may also be risk factors for MS. There has also been evidence showing that smoking may play an important role in the development of the disease. Research has shown that smoking may increase a person’s risk for developing MS and it is also associated with a more severe and rapid progression of the disease.


Potential MS cause: Infectious triggers

The initial exposure to a wide range of viruses, bacteria, and other microbes that occur during childhood are generally known to cause inflammation and demyelination (damage to the myelin sheath). This means it is possible for a virus or other form of infection to trigger the development MS.

Dozens of bacteria and viruses that have been investigated to determine if they may lead to the onset of MS, including:

  • Human herpes virus-6 (HHV-6)
  • Measles virus
  • Epstein-Barr virus (EBV)
  • Canine distemper
  • Chlamydia pneumonia

To date, none of the potential causes studies have been proven as a definitive cause of MS.


Potential MS cause: Genetic factors

Although MS is not consider to be hereditary disease, research has shown that having a first-line relative, such as a sibling or parent with multiple sclerosis may significantly increase a person’s risk of developing the disease. In fact, one study found that a child has 10-times the risk of developing MS if both of parents have it.

Studies have shown there is a significantly increased prevalence of certain genes in a population with higher rates of MS. Many researchers believe that people with multiple sclerosis are born with a genetic predisposition to certain, unknown environmental agents. Then, upon exposure to the trigger, the body begins the immune-mediated response.

Research published in June 2016 worked to identify the gene mutation responsible for the onset of multiple sclerosis. Identifying a mutation in the gene: NR1H3 — the researchers found that there was a 70% chance of developing MS when the mutation was present.


Disproved theories on the cause of MS

While there is still speculation into the mechanisms leading to the onset of multiple sclerosis, some theories have been disproved. Some of these disproved theories include:

  • Living with dogs or small pets
  • Having allergies
  • Experiencing physical trauma
  • Exposure to heavy metals such as lead or mercury
  • Consuming aspartame
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