While MS is not hereditary, having a first-degree relative such as a parent or sibling with MS does significantly increase an individual's risk of developing the disease. Studies have shown that there is a higher prevalence of certain genes in populations with higher rates of MS. Common genetic factors have also been found in some families where there is more than one person with MS. Some researchers theorize that MS develops because a person is born with a genetic predisposition to react to some environmental agent that, upon exposure, triggers an immune-mediated response. Sophisticated new techniques for identifying genes are helping to answer questions about the role of genes in the development of MS.