A new study has found that smoking boosts the relationship between the risk factor for multiple sclerosis and the disease, which makes the probability of contracting neurologic disease more than expected.

If a person has elevated levels of antibodies due to the Epstein-Barr virus, then it doubles the chances of getting the disease. Epstein-Barr virus has been found to be a herpes virus that has the potential to infect people at large and is also linked with multiple sclerosis.

Kelly Claire Simon, a Research Associate at the Harvard School of Public Health in Boston said, "Although higher antibody titers to EBV are associated with an increased risk of MS, an individual's absolute risk of MS associated with high antibody titers to EBV is still small".

Kelly and her colleagues did an assessment of 442 people suffering from MS and 865 people who were in good physical shape and without MS. All the participants were a part of three large studies.

The researcher team also evaluated whether smoking lead to an increase in MS, in a set of people who have HLA-DR15, which is an immune system gene and also associated with the boost in MS. The gene was found to be present in among 60% of the population suffering from MS.

The study is available in print in the Journal Neurology.