Developing MS is certainly not your fault and has nothing to do with your lifestyle or behaviour. You did not catch it and it is not contagious. Although we do not know why people get MS, research suggests that a combination of genetic and environmental factors may play a role.

Genetic factors
MS is not directly inherited and, unlike some conditions, there is no single gene that causes it. It is possible that a combination of genes make some people more susceptible to developing MS; however these genes are also common in the general population. So genes are only part of the story and other factors are also involved in MS.

Whilst MS can occur more than once in a family, it is more likely this will not happen. Indeed, there is only a two per cent chance of a child developing MS when a parent is affected. This risk is much lower than, for example, the risk of developing cancer or heart problems when a parent is affected.

Environmental factors
MS is more common in areas further away from the equator. It is virtually unheard of in places like Malaysia or Ecuador but relatively common in Britain, North America, Canada and Scandinavia. It is not clear why, but it is possible that something in the environment, perhaps bacteria or a virus, plays a role. No single virus has been identified as contributing to MS, but some researchers think that a common childhood virus may act as a trigger by disturbing your immune system or indirectly setting off a process whereby your immune system attacks itself. This theory remains unproven and many people who do not have MS would have also been exposed to these viruses.

Interestingly, it seems that if you move to countries further from the equator after the age of 15, your chances of developing MS still correspond to your country of origin, rather than the country you move to.