Although the exact causes and risk factors of multiple sclerosis are still unknown to modern medical science, it is believed that the disease occurs on the premises of inherited genetic dysfunctions and is triggered by certain environmental factors (either exposure to chemicals or infections with viruses or bacteria). Despite the fact that medical scientists have conducted elaborate research on multiple sclerosis over the last few years, the exact genes that render people more susceptible to developing the autoimmune disorder and the exact environmental causative agents haven't been identified yet. Medical scientists hope that in the near future they will be able not only to discover the exact causes of multiple sclerosis, but also find efficient means of preventing the occurrence of the disorder in persons with predisposition to autoimmune disorders.

According to recent studies in the field, genetic factors play a major role in the occurrence and progression of multiple sclerosis. Medical scientists inform that multiple sclerosis has a pronounced hereditary character, the genes that render people susceptible of developing the disorder being transmissible from one generation to another. Recent medical research has revealed the fact that the identical twin of a person diagnosed with multiple sclerosis has a 30 percent chance of developing the same disorder at a certain point in life. The risk of first degree relatives of persons with multiple sclerosis to develop the disorder is 50 times higher than that of persons with no family history of multiple sclerosis. Medical scientists are currently working to identify the exact genes that render persons with a family history of multiple sclerosis susceptible to developing the disorder at a certain stage in life.

Medical scientists believe that infections with viruses are also potential causes of multiple sclerosis. This belief is supported by the unequal geographic distribution of the disease (cases of multiple sclerosis are more numerous in regions of the Globe confronted with regular cases of viral diseases). In addition, scientists have established a link between multiple sclerosis and viral epidemics. According to the results of medical investigations, the overall number of multiple sclerosis cases increases during viral epidemics. In addition, certain viruses are very similar to myelin (the protein that is primarily affected by multiple sclerosis), and it is thought that such viruses confuse the immune system, determining its antibodies to target the body's healthy nerve cells covered in myelin instead of the intruding infectious agents.

The infectious organisms that are suspected to play a role in the occurrence and progression of multiple sclerosis are herpesviruses and Chlamydia pneumoniae bacteria. The HHV-6 subtype of herpesvirus (virus that causes roseola in children) has also been identified to cause severe diseases of the nervous system such as encephalitis (brain inflammation). Other subtypes of herpesviruses such as herpes simplex 1 and 2, varicella-zoster virus and cytomegalovirus also have potential of causing dysfunctions of the nervous system. Chlamydia pneumoniae, an atypical bacterium that has been linked with various inflammatory diseases is also suspected to cause multiple sclerosis. Although medical research continues, signs of infection with Chlamydia pneumoniae have been revealed in the majority of patients with multiple sclerosis.