The causes of multiple sclerosis are when myelin (the protective coating around nerves) is attacked by the individual's immune system and inflammation results, causing problems in nerve transmission. When myelin is lost or damaged, the transfer of nerve impulses to and from the brain is disrupted and nerve tissue can become inflamed. The inflammation is what causes multiple sclerosis symptoms to appear.
Inflammation also occurs with a relapse. During a relapse, an individual with MS may experience some physical disability and/or cognitive impairment, such as trouble with memory or problem solving. When the inflammation subsides, the symptoms of multiple sclerosis may subside as well. This period is known as a remission. Physical disability is one way to mark the progression of disease in multiple sclerosis. However MS can also progress silently through the loss of axons. The brain can compensate for some level of damage, so symptoms may be hidden for quite some time. Individuals actually could have multiple sclerosis, yet still feel perfectly healthy.
Heredity: Studies examining the incidence of the disease in the general population, in families, and in twins support a genetic component to MS. However, no single gene has been identified that determines susceptibility to the disease; rather, a number of genes are believed to be involved. About one quarter of all people who have MS have a relative who is also afflicted with the disease. Studies of identical twins show that MS occurs in both twins in about 25-35% of cases. This finding suggests that up to 75% of MS must be attributable to non-genetic factors and that the contribution of genetics is actually relatively minor.
Immunity: The immune system is designed to protect us from outside enemies, such as viruses or bacteria that cause illness. The immune system may also attack healthy body parts or tissues. Diseases in which this process happens are called autoimmune diseases. In multiple sclerosis, it is believed that the immune system attacks the myelin in the body.
Geography and climate: Multiple sclerosis most commonly affects people in North America, Europe, and Australia. It strikes people more frequently in locations farther away from the equator. For example, in the United States, the incidence of multiple sclerosis is much higher in northern states with temperate climates (seasonal changes) than in warmer southern states. The amount of daily sunlight exposure is a major factor in the geographical risk factors associated with developing MS. Sunlight helps the body manufacture vitamin D, which is reported lowered in those with MS. The more Northern climates have less available sunlight hours per day.
Infectious agents: Infectious agents, such as bacteria or viruses, may contribute to the development of MS. There is significant data that infection is involved in both the initiation of the disease and in damage to the nerves. Several organisms have been proposed as potential triggers, including human herpesvirus type 6 (Epstein-barr virus), Mycoplasma pneumoniae, and Chlamydia pneumoniae.
Environmental toxins: Exposure to chemical toxins, such as organic solvents, paint thinners, and pesticides, may be another possible trigger of MS. Exposure to heavy metals, such as mercury, has been implicated in MS. Mercury is believed to be one of the most toxic of all non-radioactive elements; it is widely known to affect neurological tissues. Exposure to dental amalgam (mercury) fillings has been suggested as a risk factor for developing MS.
Food allergies: Allergies and sensitivities to certain foods may also play a role in the development or exacerbation of MS. MS is most prevalent in areas where consumption of wheat gluten and milk are also high. Wheat gluten and cow's milk are common food allergens. This relationship has not been proven conclusively, but allergies may play some role in the onset or severity of MS. Components of some foods may act as triggers to the immune system, causing it to begin an inappropriate autoimmune response similar to the body's autoimmune response to bacteria and viruses. Consumption of cow's milk has also long been suspected to play a role in the development of MS. Researchers are not sure whether it is the high level of saturated fat that is harmful to people who have MS, or there may be more to the dairy connection than mere fat. One of the proteins in milk mimics a particular protein affiliated with human myelin. This milk protein could potentially trigger an autoimmune response to native myelin, leading to an MS episode.
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