What Causes MS?

Over the years, people have suggested many different causes for MS. Here are some widely known theories that have been proved incorrect.

Living with a dog or other small pet: Some years ago, canine distemper — a virus carried by dogs — was proposed as a cause of MS, but research has since ruled out household pets as the culprit.

Having allergies: There is no evidence that MS is triggered by a reaction to a specific environmental allergen. Allergies are common in the general population and can occur in people with MS.

Exposure to heavy metals: Although poisoning with heavy metals such as mercury, lead or manganese can damage the nervous system and produce symptoms such as tremor and weakness, both the process and the symptoms are different from what occurs in MS. There is no evidence that heavy metal exposure causes MS.

Experiencing physical trauma: The role of trauma in causing MS or in triggering subsequent MS — also known as attacks, exacerbations or flares — has been the subject of controversy for many years. However, research has demonstrated that there is no association between physical trauma and disease onset or progression in MS.

• A 1999 report of the Therapeutics and Technology Assessment Subcommittee of the American Academy of Neurology, based on a comprehensive study of the literature on the subject, concluded that “the evidence supports no association between physical trauma and either MS onset or MS exacerbation.” Read in the journal Neurology.
• A prospective study conducted by researchers at the University of Arizona followed 170 MS patients and 134 control-group members over a period of eight years. (A prospective study is one that follows a group of people with a given disorder over a specific period of time, beginning before the occurrence of the events being studied.) The results of this study, in the Journal of Neurology, Neurosurgery and Psychiatry, concluded that except for electrical injuries, there was no evidence of a direct relationship between traumatic injury and an MS exacerbation.
• performed at the Mayo Clinic (where there is an MS patient population for whom complete clinical records have been maintained for years) supported the Sibley group’s findings that traumatic injury is not related to exacerbation of MS. The Mayo study also indicated there is no relationship between traumatic injury and MS onset. Although this study (published in 1993) was retrospective, it was based upon the detailed clinical records of 164 long-term patients with definite MS, actively followed at the Mayo Clinic.
• The University of Arizona and Mayo Clinic studies both showed that there are more traumatic events among people with MS than in the healthy control group. Many traumas were caused by MS symptoms such as incoordination, impaired balance, or abnormalities of gait or vision. These events, however, were not precipitating factors in the onset or exacerbation of the disease.

Aspartame: No scientific evidence supports the claims that aspartame — an artificial sweetener used in many diet soft drinks and other foods — causes MS. More information about aspartame is available through the websites.