Causes of Multiple Sclerosis Scientists do not know for certain what causes multiple sclerosis. They believe that a mix of factors trigger MS. Studies support the idea that a trigger in the environment may cause MS in certain people who have a specific combination of genes. Genes carry the traits that you get from your parents. Research also suggests that ethnicity and geographic location play a role. To identify the cause of MS, research is focusing on: Immunology - the study of the body’s immune system Epidemiology - the study of disease patterns in large groups of people Genetics - understanding the genes that may not be functioning correctly in people who develop MS Infectious agents - viruses that may contribute to developing MS Understanding what causes MS will speed up the process of finding more effective ways to treat it and — ultimately — cure it. Ideally, we will find a way to prevent MS from occurring in the first place. Immunology and MS In MS, an abnormal immune response causes inflammation. This inflammation damages the central nervous system. The abnormal immune response involves many different cells. Two important types of immune cells are T cells and B cells: T cells become activated in the lymph system. The lymph system is part of the immune system. It includes bone marrow, thymus and lymph nodes. In MS, T cells enter the central nervous system through blood vessels. Once there, T cells release chemicals that cause inflammation and damage. This results in damage to nerve fibers, myelin and the cells that make it. Myelin is the insulating layer around nerves. T cells also help activate B cells and call on other immune system cells to participate in the immune attack. T regulatory cells are a type of T cell. In MS, they do not function correctly and fail to turn off inflammation. Cytotoxic or “killer” T cells directly attack and destroy cells with certain characteristics. B cells become activated with the help of T cells. B cells produce antibodies and stimulate other proteins. Antibodies are proteins that fight infections or other abnormal substances. In MS, these cause damage in the central nervous system. Researchers continue to search for other cells and processes that could be involved in MS. They want to learn more about what sets the immune system in motion in MS and how to slow or stop it. Environmental Factors of MS Although the cause of MS is not known, we are learning more about environmental factors that contribute to the risk of developing MS. No single risk factor provokes MS. Researchers believe that several factors contribute to the overall risk. Geography and Multiple Sclerosis MS diagnoses occur more frequently in areas farther from the equator. To understand why, epidemiologists are studying many factors. Epidemiologists are scientists who study disease patterns in large groups of people. They are looking at variations in: For instance, one study shows that access to healthcare in these areas could explain why MS is more prevalent there. Other studies show that people who move before the age of 15 tend to take on the risk level of the area they move to. This could either increase or lower their risk. Such data suggest people exposed to some environmental agent before puberty are more likely to develop MS later on. MS “ clusters ” are the perception that very high numbers of cases of MS have occurred in a specific time period or location. Clusters may provide clues to the environmental or genetic risk for the disease. So far, cluster studies have not produced clear evidence that one particular factor causes or triggers MS. Scientists need more studies to confirm all these theories. Vitamin D and Multiple Sclerosis Growing evidence suggests that vitamin D plays an important role in MS. Vitamin D is a nutrient needed for good health. Sun exposure is a natural source of vitamin D. Scientists have identified a low vitamin D level in the blood as a risk factor for developing MS. Some researchers believe that sun exposure may have a link to MS. It could help to explain why people with MS tend to live in northern regions of the planet. People who live closer to the equator are exposed to greater amounts of sunlight year-round. As a result, they tend to have a higher level of naturally-produced vitamin D. Researchers think this supports immune function. It may help protect against immune-mediated diseases like MS. They are trying to find out if taking vitamin D supplements helps prevent and manage MS. If you have questions about taking supplements, ask your healthcare provider. Smoking and Multiple Sclerosis More and more evidence also indicates that smoking plays an important role in MS. Studies show that smoking increases a person’s risk of MS. It is associated with more severe disease and faster progression. Fortunately, the evidence also suggests that quitting helps slow down disability. This includes quitting both before and after the onset of MS. Obesity and Multiple Sclerosis Several studies show that obesity in childhood and adolescence increases the risk of MS. These studies highlight a risk, particularly in girls. Other studies show that obesity in early adulthood may also contribute to an increased risk of MS. Obesity may contribute to inflammation and more MS activity in those already diagnosed with MS. This can include a rise in relapses and lesions on MRI. Infectious Factors Scientists are investigating the role of many viruses and bacteria in the development of MS. These viruses and bacteria include: EBV causes mononucleosis. It has received significant attention in recent years. A growing number of research findings show that a previous EBV infection adds to the risk of MS. This does not mean that MS is an infectious disease. However, inactive viruses may play a role in triggering MS symptoms and activity. And while the viruses that are potentially involved in the development of MS — such as EBV and HHV-6 — are infectious, MS itself is not. MS is not contagious.Is MS Genetic or Hereditary? MS is not an inherited disease. It is not passed down from generation to generation. But people can inherit genetic risk. This means that MS is not genetic in the simple way that black hair or dimples are. In fact, researchers have identified about 200 genes that each contribute slightly to the overall risk of developing MS. Studies of twins have contributed to the belief that genes do play some role. In the general population, the risk of developing MS is about 1 in 333. In identical twins, if one twin has MS, the risk that the other twin will develop MS is about 1 in 4. The risk of developing MS also increases when other first-degree relatives (parents, siblings and children) have MS, but far less than in identical twins. Researchers are trying to better understand how genetic risk contributes to the development of MS. Unproven Theories About Causation of MS Researchers have investigated many possible causes of MS without turning up evidence of a link. These theories include: Environmental allergies Exposure to household pets Exposure to heavy metals: lead, manganese and mercury (including that in amalgam tooth fillings) Chemical solvents Some of these theories surfaced because people had their first MS symptoms after being exposed to something new in their environment. At this point, further research is warranted to understand if and how toxins and environmental substances play a role in the development of MS. If you have any questions about your exposure, ask your healthcare provider. Scientists do not know for certain what causes multiple sclerosis. They believe that a mix of factors trigger MS. Studies support the idea that a trigger in the environment may cause MS in certain people who have a specific combination of genes. Genes carry the traits that you get from your parents. Research also suggests that ethnicity and geographic location play a role. To identify the cause of MS, research is focusing on: Immunology - the study of the body’s immune system Epidemiology - the study of disease patterns in large groups of people Genetics - understanding the genes that may not be functioning correctly in people who develop MS Infectious agents - viruses that may contribute to developing MS Understanding what causes MS will speed up the process of finding more effective ways to treat it and — ultimately — cure it. Ideally, we will find a way to prevent MS from occurring in the first place. Immunology and MS In MS, an abnormal immune response causes inflammation. This inflammation damages the central nervous system. The abnormal immune response involves many different cells. Two important types of immune cells are T cells and B cells: T cells become activated in the lymph system. The lymph system is part of the immune system. It includes bone marrow, thymus and lymph nodes. In MS, T cells enter the central nervous system through blood vessels. Once there, T cells release chemicals that cause inflammation and damage. This results in damage to nerve fibers, myelin and the cells that make it. Myelin is the insulating layer around nerves. T cells also help activate B cells and call on other immune system cells to participate in the immune attack. T regulatory cells are a type of T cell. In MS, they do not function correctly and fail to turn off inflammation. Cytotoxic or “killer” T cells directly attack and destroy cells with certain characteristics. B cells become activated with the help of T cells. B cells produce antibodies and stimulate other proteins. Antibodies are proteins that fight infections or other abnormal substances. In MS, these cause damage in the central nervous system. Researchers continue to search for other cells and processes that could be involved in MS. They want to learn more about what sets the immune system in motion in MS and how to slow or stop it. Environmental Factors of MS Although the cause of MS is not known, we are learning more about environmental factors that contribute to the risk of developing MS. No single risk factor provokes MS. Researchers believe that several factors contribute to the overall risk. Geography and Multiple Sclerosis MS diagnoses occur more frequently in areas farther from the equator. To understand why, epidemiologists are studying many factors. Epidemiologists are scientists who study disease patterns in large groups of people. They are looking at variations in: For instance, one study shows that access to healthcare in these areas could explain why MS is more prevalent there. Other studies show that people who move before the age of 15 tend to take on the risk level of the area they move to. This could either increase or lower their risk. Such data suggest people exposed to some environmental agent before puberty are more likely to develop MS later on. MS “ clusters ” are the perception that very high numbers of cases of MS have occurred in a specific time period or location. Clusters may provide clues to the environmental or genetic risk for the disease. So far, cluster studies have not produced clear evidence that one particular factor causes or triggers MS. Scientists need more studies to confirm all these theories. Vitamin D and Multiple Sclerosis Growing evidence suggests that vitamin D plays an important role in MS. Vitamin D is a nutrient needed for good health. Sun exposure is a natural source of vitamin D. Scientists have identified a low vitamin D level in the blood as a risk factor for developing MS. Some researchers believe that sun exposure may have a link to MS. It could help to explain why people with MS tend to live in northern regions of the planet. People who live closer to the equator are exposed to greater amounts of sunlight year-round. As a result, they tend to have a higher level of naturally-produced vitamin D. Researchers think this supports immune function. It may help protect against immune-mediated diseases like MS. They are trying to find out if taking vitamin D supplements helps prevent and manage MS. If you have questions about taking supplements, ask your healthcare provider. Smoking and Multiple Sclerosis More and more evidence also indicates that smoking plays an important role in MS. Studies show that smoking increases a person’s risk of MS. It is associated with more severe disease and faster progression. Fortunately, the evidence also suggests that quitting helps slow down disability. This includes quitting both before and after the onset of MS. Obesity and Multiple Sclerosis Several studies show that obesity in childhood and adolescence increases the risk of MS. These studies highlight a risk, particularly in girls. Other studies show that obesity in early adulthood may also contribute to an increased risk of MS. Obesity may contribute to inflammation and more MS activity in those already diagnosed with MS. This can include a rise in relapses and lesions on MRI. Infectious Factors Scientists are investigating the role of many viruses and bacteria in the development of MS. These viruses and bacteria include: EBV causes mononucleosis. It has received significant attention in recent years. A growing number of research findings show that a previous EBV infection adds to the risk of MS. This does not mean that MS is an infectious disease. However, inactive viruses may play a role in triggering MS symptoms and activity. And while the viruses that are potentially involved in the development of MS — such as EBV and HHV-6 — are infectious, MS itself is not. MS is not contagious.Is MS Genetic or Hereditary? MS is not an inherited disease. It is not passed down from generation to generation. But people can inherit genetic risk. This means that MS is not genetic in the simple way that black hair or dimples are. In fact, researchers have identified about 200 genes that each contribute slightly to the overall risk of developing MS. Studies of twins have contributed to the belief that genes do play some role. In the general population, the risk of developing MS is about 1 in 333. In identical twins, if one twin has MS, the risk that the other twin will develop MS is about 1 in 4. The risk of developing MS also increases when other first-degree relatives (parents, siblings and children) have MS, but far less than in identical twins. Researchers are trying to better understand how genetic risk contributes to the development of MS. Unproven Theories About Causation of MS Researchers have investigated many possible causes of MS without turning up evidence of a link. These theories include: Environmental allergies Exposure to household pets Exposure to heavy metals: lead, manganese and mercury (including that in amalgam tooth fillings) Chemical solvents Some of these theories surfaced because people had their first MS symptoms after being exposed to something new in their environment. At this point, further research is warranted to understand if and how toxins and environmental substances play a role in the development of MS. If you have any questions about your exposure, ask your healthcare provider.