New here? Register | Already registered? Sign in Search
     Print     Text Size   A  A  A 

What Causes MS?

Although multiple sclerosis has been recognized as a disease since the mid-1800s, researchers still aren't sure exactly what causes MS.

MS affects over 400,000 people in the United States and up to 2.5 million people worldwide. And women are more likely to get it than men. In fact, about 70% of the MS population is female.

Since most people are diagnosed before they turn 30, MS has been called the most common disability-causing illness for people under 45.

Immune Response

MS is an autoimmune disease. In autoimmune diseases, the body mistakes some part of itself as a foreign invader. In MS, the body mistakes the protective covering of nerve fibers, the myelin sheath, for an unwelcome guest.

One theory is that MS is initially caused by the body overreacting to a foreign invader, which could cause the immune system to attack myelin — in addition to the invading virus or bacteria — even after the foreign invader is gone.


The place where you grew up may also influence how likely you are to get multiple sclerosis. Multiple sclerosis is more common in cooler areas of the globe. In the United States, northern states have higher rates of MS than southern states, and Canada has a rate of MS double that of the US.

Heredity Factors as Causes of MS

Our genes may also play a key role in MS. People from different ethnic groups have different tendencies to develop MS: People of European descent are twice as likely to have MS as African Americans and Asian Americans.

MS also occurs more often in relatives of people with MS

Children, siblings, and non-identical twins of people with MS have a one in 100 to one in 40 chance of having MS themselves. The chances of the identical twin of someone with MS also having MS increase greatly — to one in four. However, having MS shouldn't discourage anyone from enjoying the rewards of parenthood, but speak with your doctor before making any decisions.

Join MS ActiveSource.

Register for benefits, including:

  • Free MS Fitness or Yoga DVD
  • One-on-one
    peer mentors
  • Your own personal
  • Monthly e-newsletter

or Sign In
Ongoing support
means you're
not alone.

Now you can connect with free
support and resources for living
with MS, including:

  • Personalized Patient
  • Peer Mentor
  • MS Events
Live well. Stay active.

Get tips on:

  • Exercise
  • Healthy eating
    and recipes
  • Free MS Fitness
    or Yoga DVD

Call an ActiveSource Coordinator at 1-800-456-2255
Monday – Friday, 8:30 AM – 8:00 PM ET