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In some ways, it seems like researchers know more about what doesn’t cause multiple sclerosis than about what might. With several disproved theories, it almost seems like there is no root cause of the immune response.

Because multiple sclerosis is such a mystery in so many ways, doctors and other researchers have spent endless time and effort trying to determine the cause of the initial immune response that leads to the disease. And in the midst of that research, they have come up with a number of theories, some more realistic than others. However, most theories have already been disproved, which leads them right back to square one.

In order to understand the reason some of these theories were first considered, it’s important to recognize how the disease itself works and what lies behind the symptoms multiple sclerosis patients experience.

What causes multiple sclerosis?

While the answer to that question has yet to be found, the cause of the symptoms of MS are due to an immune response, which makes MS an autoimmune disease. In MS, the antibodies that are created to protect the body against viruses and bacteria instead launch an attack on the central nervous system, or more specifically, on the myelin.

Myelin is a substance made of fat and protein that wraps around the nerve fibers in the brain and spinal cord. It has a dual purpose:

  1. To insulate the nerves against potential damage
  2. To speed up the electrical impulses passed through the central nervous system (CNS)

When the myelin is attacked, it is destroyed, both slowing the nervous responses and damaging various areas of the nerves. This also leads to inflammation that further affects the performance of the CNS. Nerve damage can’t be repaired and causes permanent disability to the MS patient. For most MS patients, the disease starts out with relapses and remissions, so symptoms are not constant. But this usually advances into the progressive disease that leaves a permanent mark on the patient’s ability to get around, as well as affecting several other parts of the nervous system.

Multiple theories

Again, no one has discovered why the myelin is attacked in the first place or what causes the autoimmune response. However, several theories of how this is triggered have been tested and failed to produce results. There are at least five rejected theories about multiple sclerosis that were once thought to be the absolute answer to curing the disease.
  1. Heavy Metal Exposure. There are a number of heavy metals that are poisonous and can lead to damage in the nervous system. For example, mercury, lead, and manganese can all create symptoms similar to those found in MS patients, such as trembling and weakness in the limbs. However, studies show that the process by which these metals damage the nerves is different than what happens in MS, thereby disproving that heavy metal exposure causes the immune response that triggers MS.

  2. Allergies. For a time, it was believed hat certain environmental allergens caused the immune system to malfunction. Allergies are a common issue, affecting at least a quarter of the population. However, based on research, the prevalence of allergies, and the relatively low number of people who develop MS, there has been no link made between having an allergy and developing the disease.

  3. Dogs and Pets. One of the most common diseases found in dogs is canine distemper, which can be transmitted to humans. This is something dogs are vaccinated for, but at one time, the transmission to humans was seen as a potential cause of multiple sclerosis. Research has not shown this to be the case, and there appears to be no link between any animal-borne disease in pets and the development of MS.

  4. Aspartame. Artificial sweeteners constantly receive harsh criticism, with links to various being theorized. In the case of aspartame, it’s used in a number of diet colas and other foods to replace sugar. At one point, it was suggested that aspartame played a role in triggering MS, but several studies have shown otherwise over time.

  5. Physical Trauma. Many have suggested through the years that some sort of physical trauma – a car accident, broken bones, muscle or tissue damage, etc. – may be the culprit behind either the onset of the disease or its progression. However, multiple studies by the American Academy of Neurology, the University of Arizona, and the Mayo Clinic all reach the same conclusive evidence that experiencing physical trauma is in no way related to triggering the initial symptoms of MS, enhancing the symptoms, or causing the disease to progress faster.

New studies are inconclusive

One new theory that is being studied is inconclusive and considers that the onset of symptoms has nothing to do with an autoimmune response and everything to do with the death of cells that make myelin.

In a young patient who died suddenly in the midst of a relapse, it was found that new lesions in the brain were filled with dying myelin cells but contained no antibodies or lymphocytes created to attack the myelin. This provides a new potential problem that could be the root cause of multiple sclerosis, though there is very little evidence and very little opportunity to study any lesions that are less than a day old.

Another theory has linked the presence of Epstein-Barr (EBV, the virus that causes mononucleosis) and chickenpox with triggering the disease. Once exposed to these herpes viruses, they never leave the body. While more than ninety percent of the population is exposed to at least one of these, nearly one hundred percent of MS patients carry the virus from exposure. Researchers believe that, while a patient must have some sort of predisposition to develop multiple sclerosis, these viruses are related to the actual onset.


In some ways, it seems like researchers know more about what doesn’t cause multiple sclerosis than about what might. With several disproved theories, it almost seems like there is no root cause of the immune response. With continued research, the hope is to eventually find a cause that will then lead to a cure, since the disease is degenerative and causes long term damage to the body.