What causes MS?

Is MS a genetic or hereditary condition?

MS is not directly passed from parent to child. There's no single gene that causes it. Over 200 genes might affect your chances of getting MS. But genes are only part of the story.

MS can happen more than once in a family, but it's much more likely this will nothappen. There's only about a 1.5% chance of a child developing MS when their mother or father has it (that means around one in 67 get it). There's around a 2.7% chance that you'll get MS if your brother or sister has it (around one in 37 get it). In 2014 a very large study found that MS may be even less likely to be passed on than these figures suggest.

Are you born with MS?

You’re not born with symptoms of MS. If you develop MS it’s usually diagnosed in your 30s or 40s. But it can also develop earlier or later than that. There’s currently no way to tell for certain whether someone will develop MS later in life.

Read more about genetics and MS

How did the MS gene spread?

There's no single 'MS gene', but researchers have traced the origins of some of the genes linked to MS by examining ancient human DNA. They found these genes were introduced to Europe around 5,000 years ago.

It’s thought the changes in the genes of these ancestors were beneficial at the time. Many of the genes are linked to the immune system, so they might have protected against catching infections from their sheep and cattle. But they also increased the risk of developing MS.

Most research on genes and MS has involved people of White European descent. But one study, called the ADAMS study, has shown that the most important genes for MS risk have a similar impact for people with African and South Asian ancestry as well.

MS risk factors

MS risk factors include how old you are, your biological sex, smoking, someone in your family also having MS (genes), and things in your environment. For example, some common infections and vitamin D levels might affect the risk of developing MS. But there isn’t just a single cause of MS that we know of.

Can environmental and lifestyle factors cause MS?

There's no single cause of MS that we know of. MS environmental factors and lifestyle factors are things in our lives and the world around us that might affect our risk of getting MS, like:

• where we grow up
• infections
• vitamin D
• smoking 
• obesity

Does where you live affect MS risk?

MS is less common in tropical countries near the equator that get lots of sunshine. More people have MS in places further away from the equator like the UK, and that's true no matter what your ethnic background is. Other countries where MS is more common include Canada, the US, Scandinavia, southern Australia and New Zealand.

Infections

There's evidence that some viruses, and maybe bacteria, play a part in triggering MS.

A common virus called Epstein Barr virus (it causes glandular fever) has been linked to MS. Most people have had this virus but they never get MS. This shows that, like genes, infections might play a role but they aren't the whole story.

Vitamin D

There's more and more evidence that low levels of vitamin D, especially before you become an adult, could be a factor in why people get MS.

Our skin makes most of our vitamin D when we're out in the summer sun. We also get some from food like oily fish, eggs, spreads and breakfast cereals with added vitamin D in them. You can also get extra vitamin D from supplements (but too much can be harmful).

A blood test can show if your levels of vitamin D are low.

Read more about vitamin D and MS

Smoking

Studies show people who smoke are more likely to get MS. It’s less certain if passive smoking also affects the risk (breathing in other people’s smoke). Some studies have found that passive smoking might increase the risk if you have MS in your family.

If you have relapsing MS, studies show that stopping smoking could slow down the rate at which your symptoms or disability gets worse and how fast relapsing remitting MS changes to secondary progressive MS.

Obesity

Studies show there could be a link between getting MS and being very overweight (obese), especially if someone was obese as a child or young adult.

This might be because obese people are often low in vitamin D, which may increase the risk of developing MS. Obesity can also make your immune system overactive and cause inflammation in your body. There may be other reasons we don't understand yet.

Of course, not all people who are very overweight get MS, and having MS doesn't mean you are or were obese. But if your risk of getting MS is on your mind, perhaps because a close relative has it, then weight could be a risk factor you can change.

How do you get MS?

MS isn't directly passed on. While over 200 genes might affect your chances of getting MS, genetics only play a part. Having someone else in your family with MS increases your risk slightly, but the chances are still low. Having a parent with MS gives you about a 1.5% risk, and having a brother or sister with MS increases it to around 2.7%.

The exact cause of MS is unknown but there are some things that could increase your risk of getting MS. Age, genetics, biological sex, obesity and smoking play a role. Things connected to your environment like infections and vitamin D levels can also play a part.

Can I reduce my risk of developing MS? 

We’re learning more about what causes MS. It’s likely to be a mix of genes, something in your environment and lifestyle factors. Because there’s no single cause of MS, there’s no one way to stop someone from developing MS altogether.

There are some things that may reduce your risk of developing MS. These include getting enough vitamin D, not smoking and maintaining a healthy weight.

You can’t control every factor associated with an increased risk of MS. Things like genetics are out of our control. And it’s no-one's fault that they develop MS.

Can you prevent MS?

Making healthy choices, like stopping smoking and maintaining a healthy weight, can reduce someone’s risk of developing MS. Research is looking into these and other possible risk factors, including common viruses like Epstein Barre. But at the moment there’s no way to completely prevent someone from getting the condition.

We want fewer people to develop MS in the future. MS prevention is a key focus of our research strategy. And we founded the UK MS Prevention Taskforce to make progress in this area.

Read more about genetic research and MS