What causes MS?

The causes of MS are likely to be a mix of genes, something in your environment and lifestyle factors. Read on to find out the potential causes of MS.

Is MS a genetic or hereditary condition?

MS is not directly inherited 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 not happen. 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 only 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 whether someone will develop MS later in life.

Read more about genetics and MS

How did the MS gene spread?

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 our 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.

Read more about this research  

MS risk factors

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

Environmental factors

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 Britain, 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, can help trigger 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

Lifestyle

Smoking

Studies show you're more likely to get MS if you smoke. Less certain is the risk of passive smoking. Some studies have found that if you have MS in your family, your risk of getting it too might go up if you're exposed to passive smoking (breathing in other people's smoke).

If you have relapsing MS and you stop smoking it can slow down how fast your MS might change to secondary progressive MS.

Obesity

Studies show that getting MS could be linked to being very overweight (obese), especially when you were a child or young adult. This might be because obese people are often low in vitamin D. 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 your weight is 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.