Causes of MS
No one knows the exact cause of MS, but it is likely that a mixture of genetic and environmental factors play a role.
Genes and family history
MS is not directly inherited - unlike some conditions, like cystic fibrosis, for example, there is no single gene that causes it.
It's likely that a combination of genes make some people more susceptible to developing MS, but not everyone with this gene combination will develop MS. Genes are only part of the story.
While MS can occur more than once in a family, it is more likely this will not happen. There's only around a two per cent chance of a child developing MS when a parent is affected.
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, Scandinavia, southern Australia and New Zealand.
It is not clear why people further away from the equator are more likely to get MS, but it is possible that something in the environment, perhaps bacteria or a virus, plays a role.
No single virus has been identified as definitely contributing to MS, but there is growing evidence that a common childhood virus, such as Epstein Barr virus (which can cause glandular fever), may act as a trigger.
This theory is still unproven and many people who do not have MS would have also been exposed to these viruses, so just like genes, they are unlikely to be the whole story.
There is also a growing amount of research that suggests that a lack of vitamin D could be a factor in causing MS.
We get most of our vitamin D from exposure to sunlight. Low levels of vitamin D have been linked to higher numbers of people developing many different conditions, including MS.
Read more about vitamin D in our research section.