Multiple sclerosis: a plain-language guide

Brain and nerves, Medical Conditions
16m read

Multiple sclerosis, usually shortened to MS, is a long-term condition in which the immune system attacks the protective covering around nerve fibers in the brain and spinal cord, causing symptoms that differ widely from one person to another [1,2].

This page provides general information. It does not replace advice from a doctor or another qualified healthcare professional.

Key facts

  • About 2.9 million people around the world are living with MS, and roughly one person is diagnosed every five minutes [5,6].
  • MS is two to three times more common in women than in men, and it is usually diagnosed between the ages of 20 and 50 [2,7].
  • MS becomes more common the further a country lies from the equator, which is one reason vitamin D and sunlight are studied as risk factors [2,7].
  • Having had the Epstein-Barr virus is now the strongest known environmental risk factor for MS, though almost everyone catches that virus and the large majority never develop MS [2,12,13].
  • There is no single test for MS. Diagnosis combines the history, a physical examination, MRI scans and laboratory results, following the 2024 revised McDonald criteria [3,14].
  • There is no cure, and treatment has changed a great deal. More than a dozen disease-modifying therapies now reduce relapses and new areas of damage, and UK specialists advise starting treatment as early as possible in people with active MS [1,14,15].

On this page

What is multiple sclerosis?

MS affects the brain and spinal cord, together called the central nervous system [1].

Nerves carry messages as electrical signals. Each nerve fiber works like a wire, and around it is myelin: protein and fat that acts like the insulation on a cable, helping signals travel quickly [2]. In MS the immune system, which normally fights infections, attacks that myelin by mistake. That is what autoimmune means. Damaged patches heal as scar-like areas, which is what sclerosis describes, and show on scans as lesions. Nerve fibers are harmed too, so signals slow or stop [2].

MS follows one of five courses [2]:

  • Relapsing-remitting MS: symptoms flare in episodes called relapses, then improve fully or partly. Around 85 in 100 people start here [8].
  • Secondary progressive MS: relapses become rarer or stop, and disability slowly increases [1].
  • Primary progressive MS: worsens gradually from the start, in 10 to 15 of every 100 people [8].
  • Clinically isolated syndrome, a first single episode, and radiologically isolated syndrome, a scan that looks like MS without symptoms [2].

The older idea that MS is either purely relapsing or purely progressive has given way to something more accurate. Specialists now treat it as one condition with a relapsing part and a progressive part whose balance shifts over time, so damage continues quietly between relapses [3,15]. MS is not CIDP, which harms myelin in the nerves outside the brain and spinal cord [2].

How common is it?

The Atlas of MS, from the MS International Federation, estimates about 2.9 million people worldwide live with MS. Most of the rise over the past decade reflects better detection and longer survival rather than growing risk, and the count includes only those diagnosed [5,6,10].

Prevalence means how many people have a condition at one time; incidence means new cases in a year [7]. Incidence is about 2.1 per 100,000 a year across 81 reporting countries, and at least 30,000 children and teenagers have MS [5].

Prevalence rises with distance from the equator: about 1 in 400 people in the United States and Canada, against 1 in 263,000 in Kenya [6,7]. Access to care shapes those numbers too.

MS is two to three times more common in women than men, and is usually diagnosed between 20 and 50 [2,7]. Over 150,000 people in the United Kingdom live with MS [10].

What causes it?

The cause is not known, and several factors probably combine [9].

A gene is an instruction inside cells. MS is not inherited in a predictable way, most people who develop it have no family history, and the gene variants involved mostly affect the immune system [2,9]. A parent or sibling with MS raises the risk [1].

The strongest environmental link is Epstein-Barr virus, which causes glandular fever. In a study of more than 10 million young adults in the United States military, 955 of whom developed MS, the risk was 32 times higher after Epstein-Barr infection and not raised after other viruses [12]. Almost everyone catches this virus and the large majority never develop MS, so it is one piece, not the whole answer [2,13].

Three other factors carry good evidence: time in the sun and higher vitamin D levels are linked to lower risk [2]; smokers are about twice as likely to develop MS, and smoking speeds progression [1,2]; and childhood obesity raises the risk, most strongly in girls [9].

Nothing a person did caused it [9].

What are the symptoms?

Everyone with MS is affected differently, depending on which parts of the brain and spinal cord are damaged [1,2].

  • Fatigue, a persistent lack of energy rather than ordinary tiredness, often worse in hot weather [2]. Estimates of how many people it affects range from 37 to 78 percent, and it is linked to lower quality of life and difficulty staying in work [20]. Guidance tells clinicians to ask about it directly [14].
  • Vision problems, including loss of vision in one eye with pain on moving it: that is optic neuritis, inflammation of the nerve between eye and brain [2,14].
  • Changes in sensation: numbness, tingling or pain in the limbs, trunk or face, sometimes running down the back on bending the neck [2,14].
  • Weakness, stiffness and poor balance; stiffness with painful spasms is called spasticity [2,14].
  • Bladder, bowel and sexual problems [1,2].
  • Changes in thinking, memory and mood, in up to 75 percent of people [2].

When to seek urgent help. A relapse means new or worsening symptoms lasting more than 24 hours after at least a month of stability, not explained by an infection. Contact the MS team without delay, since relapse treatment should be considered within 14 days [14]. Seek emergency help for sudden weakness or numbness in one arm, sudden loss of vision or sudden loss of balance, which can be signs of a stroke [1].

How is it diagnosed?

A family doctor who suspects MS refers the person to a neurologist, a brain and nerve specialist [1].

There is no single test [1,2]. Diagnosis combines the history and an examination of movement, coordination, vision, balance and reflexes with scans and laboratory results, following the 2024 revised McDonald criteria published in September 2025 [3,14]. Tests include:

  • MRI scans of the brain and spinal cord to look for lesions, sometimes with a dye showing which areas are actively inflamed.
  • A lumbar puncture, where a needle in the lower back takes fluid from around the spinal cord under local anesthetic. Laboratories look for oligoclonal bands, antibody bands in that fluid but not the blood, or a newer alternative, the kappa free light chain index [4].

The revisions added the optic nerve as a fifth area that can count toward a diagnosis [3,4]. Diagnosis is now much faster: updates since 2001 have cut the average time from first symptoms by roughly 75 percent, from about four years to one [4]. It can still be slow, or wrong: misdiagnosis may affect up to 20 percent of people given the diagnosis [2].

How is it treated?

There is no cure. Treatment has three parts: medicines that change the course, treatment of relapses, and care for symptoms [1].

Disease-modifying therapies, or DMTs, reduce how many relapses a person has, how severe they are, and how many new lesions appear on scans. They do not repair damage already done, which is why starting early counts [1,2,15]. Grouped by how they work [14]:

  • Removing B cells, a type of immune cell: ocrelizumab, ofatumumab, ublituximab.
  • Keeping immune cells in the lymph nodes: fingolimod, siponimod, ponesimod, ozanimod.
  • Blocking immune cells from entering the central nervous system: natalizumab, effective but with a monitored risk of a serious brain infection.
  • Resetting the immune system in short courses: cladribine, alemtuzumab.
  • Changing how immune cells behave: dimethyl fumarate, diroximel fumarate, teriflunomide.
  • Older injections: beta interferons, glatiramer acetate.

Which medicine suits a person depends on the pattern of their MS and on safety, and availability differs sharply between countries and health systems [5,6,14].

Earlier and stronger treatment is the clearest change of the last decade. UK specialists advise offering a DMT as early as possible in active MS, and considering a higher-efficacy medicine first rather than escalating later [15]. Tolebrutinib, a tablet blocking an enzyme called Bruton’s tyrosine kinase, was approved in the European Union in June 2026 for secondary progressive MS without recent relapses, and refused in the United States in December 2025 [16,17].

Relapses. Not every relapse needs steroids. Where one affects usual activities, England recommends methylprednisolone 0.5 g by mouth daily for five days. Steroids speed recovery but do not change the long-term course [2,14].

Symptom treatment and rehabilitation matters as much: medicines and support for fatigue, baclofen then gabapentin for spasticity, treatment for nerve pain, help with bladder problems, physiotherapy, occupational therapy, talking therapy, and mobility aids or home adaptations [1,14].

Living with multiple sclerosis

Care is shared between a neurologist, an MS specialist nurse, a physiotherapist and an occupational therapist. Guidance says everyone with MS should have one named contact coordinating it, and a full review yearly [1,14].

Things that help: not smoking, exercise, up-to-date vaccinations, and noting new or changing symptoms [8,14]. MS should not stop someone planning a family: fertility is not affected and pregnancy does not increase the risk of progression, though relapses may rise for three to six months after birth and some DMTs need reviewing before conception [14,15].

How much MS affects a person cannot be predicted [1]. For some the effect on daily life stays small; others adapt with mobility aids, shorter hours or more help at home. Most people with MS live into old age, with life expectancy on average a few years less than the general population, and survival is improving [1,11].

Thinking about a clinical trial?

Clinical trials test whether a treatment works and whether it is safe. MS is an active research area, so studies come up often. It helps to decide in steps.

1. Understand what the study is asking

  • what the researchers want to learn, and what the treatment is compared with, perhaps a placebo or an existing DMT
  • how long it lasts, often two years or more
  • what visits and tests are involved, and how far you would travel
  • the possible benefits and risks, and what happens to your treatment at the end

2. Consider possible medical suitability

Every trial has rules about who can take part, called eligibility criteria. For an MS study these might include a diagnosis confirmed against the McDonald criteria, a particular pattern such as relapsing-remitting or non-relapsing secondary progressive MS, recent relapses or new lesions on scans, and time off certain other treatments first.

trialport’s medifit helps people consider information related to possible medical suitability. It does not diagnose a condition, confirm eligibility or replace formal screening by the study team.

Explore multiple sclerosis clinical trials through trialport

3. Consider whether participation fits your life

A study can look right on paper and still be hard in practice:

  • how many visits there are, how long each takes, and who would come with you
  • work, school or caring responsibilities, and time off needed
  • fatigue, and how a long clinic day affects the rest of the week
  • how you feel about pausing a treatment that works, and about repeated scans

trialport’s readifit helps people reflect on their understanding, motivation, time, routines, support, emotions and practical arrangements.

4. Ask questions before deciding

  • Why is this study being done, and what is already known about the treatment?
  • What exactly would I need to do, and how often?
  • Could I receive a placebo, a dummy treatment with no active medicine used so results can be compared fairly? How likely is that here?
  • Would I have to stop my current DMT, and what if I relapse?
  • What are the known risks, and what is still unknown?
  • How will you measure whether it is working, and will you tell me?
  • Can I leave after joining, and what happens to my care then?
  • Are travel costs covered, and could I keep the treatment afterward?

Taking part is voluntary. A person can ask questions, speak with people they trust and choose not to participate.

Search for clinical trials at app.trialport.com.

Current research

Four areas are moving fast:

  • Blocking Bruton’s tyrosine kinase. These tablets are designed to reach the brain and act on inflammation that continues without relapses. Tolebrutinib is approved in the European Union, Australia and the United Arab Emirates [16,17].
  • Repairing myelin. A phase 2 trial gave 70 people with relapsing MS two existing medicines, metformin and clemastine, for six months. Signals from eye to brain held steady in the treated group and slowed in the placebo group. Disability and vision did not differ, larger studies are needed, and neither medicine is licensed for it [18].
  • Targeting the Epstein-Barr virus. Researchers are testing vaccines, immune cells trained to kill infected cells, and treatments aimed at B cells the virus alters [13].
  • Engineered immune cells. In one early study, five people with progressive MS were given CAR-T cells, immune cells modified to seek out antibody-producing cells. The treatment reached the fluid around the brain and reduced those cells, and all five had low blood counts. Very early work, not approved [19].

Study status checked: 3 August 2026. Research moves quickly, so this list will date. For current information, search at app.trialport.com.

Support and further information

The MS International Federation links national MS organizations worldwide and is the best route to a group elsewhere [5].

In the United States, the National Multiple Sclerosis Society, Multiple Sclerosis Association of America and Multiple Sclerosis Foundation offer information and support [2]. In the United Kingdom, the MS Society runs a helpline, local groups and a forum, the MS Trust publishes free plain-language information, and MS-UK offers emotional support [1].

The NHS and NINDS pages are reliable starting points for the public [1,2]. Coverage varies by country, and some have very few MS specialists and no national group [6].

Well-known people with multiple sclerosis

The actor Selma Blair announced publicly in October 2018 that she had been diagnosed with MS, and later made a documentary about living with it. People with MS have called that openness helpful, because it showed harder days and better ones and made clear that her experience is not everyone’s [21].

In the United Kingdom, broadcaster Jane Hawkes, known as Lady Janey, was diagnosed with relapsing MS at 24 [10].

Questions people often ask

Is there a cure for MS?
No. Treatment can reduce relapses, slow disability and ease symptoms, but no medicine repairs damage already done [1,2].

Does MS mean I will end up in a wheelchair?
No. That assumption is out of date, and nobody can predict how much MS will affect an individual. For some the effect on daily life stays small; others have more severe symptoms and use mobility aids or make changes at home or work [1].

Is MS inherited?
Not in a predictable way. Most people with MS have no family history, though a close relative raises the risk [1,9].

Does the Epstein-Barr virus cause MS?
It is the strongest environmental risk factor known, and the evidence that infection comes first is strong. Almost everyone catches the virus though, and the large majority never develop MS, so other factors are involved too [12,13].

Will MS shorten my life?
Most people with MS live into old age. Life expectancy is on average a few years less than the general population, and survival is improving [1,11].

Sources

  1. National Health Service (NHS). Multiple sclerosis: symptoms, tests, types, treatment, effects on life, causes and support. Page last reviewed 16 August 2024. https://www.nhs.uk/conditions/multiple-sclerosis/ Accessed 3 August 2026.
  2. National Institute of Neurological Disorders and Stroke (NINDS), National Institutes of Health. Multiple Sclerosis (MS). Last reviewed 17 December 2025. https://www.ninds.nih.gov/health-information/disorders/multiple-sclerosis-ms Accessed 3 August 2026.
  3. Montalban X, Lebrun-Frénay C, Oh J, et al. Diagnosis of multiple sclerosis: 2024 revisions of the McDonald criteria. The Lancet Neurology. 2025;24(10):850-865. doi:10.1016/S1474-4422(25)00270-4. Record and abstract retrieved through Europe PMC, https://europepmc.org/article/MED/40975101 Accessed 3 August 2026.
  4. European Committee for Treatment and Research in Multiple Sclerosis (ECTRIMS). 2024 Revisions to McDonald Diagnostic Criteria for Multiple Sclerosis Published. Press statement, 18 September 2025. https://ectrims.eu/press/revisions-to-mcdonald-diagnostic-criteria-for-multiple-sclerosis-published/ Accessed 3 August 2026.
  5. MS International Federation. New prevalence and incidence data now available in the Atlas of MS. 21 August 2023, last updated 29 November 2023. https://www.msif.org/news/2023/08/21/new-prevalence-and-incidence-data-now-available-in-the-atlas-of-ms/ Accessed 3 August 2026.
  6. MS International Federation. Atlas of MS: number of people with MS, and the country fact sheets for the United States, Canada and Kenya. https://atlasofms.org/map/global/epidemiology/number-of-people-with-ms and https://atlasofms.org/fact-sheet/kenya Accessed 3 August 2026.
  7. MS Trust. How common is multiple sclerosis? Last updated 15 May 2024. https://mstrust.org.uk/information-support/about-ms/how-common-multiple-sclerosis Accessed 3 August 2026.
  8. MS Trust. Types of MS. Last updated 1 October 2020. https://mstrust.org.uk/information-support/about-ms/types-ms Accessed 3 August 2026.
  9. MS Trust. Causes of MS. Last updated 1 January 2022. https://mstrust.org.uk/information-support/about-ms/causes-ms Accessed 3 August 2026.
  10. MS Society (UK). Number of people living with MS in UK increases. 14 May 2024. https://www.mssociety.org.uk/research/news/number-people-living-ms-uk-increases Accessed 3 August 2026.
  11. University College London. Multiple sclerosis doubles in prevalence while survival rates improve. 23 March 2026, reporting a study by Palladino R, Ciccarelli O and colleagues published in JAMA Neurology. https://www.ucl.ac.uk/news/2026/mar/multiple-sclerosis-doubles-prevalence-while-survival-rates-improve Accessed 3 August 2026.
  12. Bjornevik K, Cortese M, Healy BC, et al. Longitudinal analysis reveals high prevalence of Epstein-Barr virus associated with multiple sclerosis. Science. 2022;375(6578):296-301. doi:10.1126/science.abj8222. Abstract retrieved through Europe PMC, https://europepmc.org/article/MED/35025605 Accessed 3 August 2026.
  13. Lünemann JD, Münz C. Epstein-Barr virus and multiple sclerosis: from associations to mechanisms to potential therapies. The Lancet Neurology. 2026;25(9):755-763. doi:10.1016/S1474-4422(26)00177-8. Abstract retrieved through Europe PMC, https://europepmc.org/article/MED/42320500 Accessed 3 August 2026.
  14. National Institute for Health and Care Excellence (NICE). Multiple sclerosis in adults: management. NICE guideline NG220, published 22 June 2022, last updated 3 June 2026. https://www.nice.org.uk/guidance/ng220/chapter/Recommendations Accessed 3 August 2026.
  15. Rashid W, Ciccarelli O, Leary SM, et al, on behalf of the Association of British Neurologists Multiple Sclerosis and Neuroinflammation Advisory Group. Using disease-modifying treatments in multiple sclerosis: Association of British Neurologists (ABN) 2024 guidance. Practical Neurology. 2024. doi:10.1136/pn-2024-004228. Author accepted manuscript read in full at https://discovery.ucl.ac.uk/id/eprint/10201035/1/Ciccarelli_DMT_Guidance_final_revisions_030924.pdf Accessed 3 August 2026.
  16. Sanofi. Sanofi’s Cenrifki (tolebrutinib) approved in the EU as the first disability-targeting medicine for secondary progressive multiple sclerosis without relapses. Press release, 23 June 2026. https://www.sanofi.com/en/media-room/press-releases/2026/2026-06-23-05-00-00-3315699 Accessed 3 August 2026.
  17. Sanofi. Sanofi provides update on tolebrutinib regulatory submission in non-relapsing secondary progressive multiple sclerosis. Press release, 24 December 2025. https://www.sanofi.com/en/media-room/press-releases/2025/2025-12-24-06-00-00-3210238 Accessed 3 August 2026.
  18. MS Society (UK). Trial results suggest drug combo could boost myelin repair in relapsing MS. 26 September 2025. https://www.mssociety.org.uk/research/news/trial-results-suggest-drug-combo-could-boost-myelin-repair-relapsing-ms Accessed 3 August 2026.
  19. Qin C, Dong MH, Zhou LQ, et al. Anti-BCMA CAR-T therapy in patients with progressive multiple sclerosis. Cell. 2025;188(23):6414-6423.e11. doi:10.1016/j.cell.2025.09.020. Abstract retrieved through Europe PMC, https://europepmc.org/article/MED/41101309 Accessed 3 August 2026.
  20. Oliva Ramirez A, Keenan A, Kalau O, Worthington E, Cohen L, Singh S. Prevalence and burden of multiple sclerosis-related fatigue: a systematic literature review. BMC Neurology. 2021;21:468. doi:10.1186/s12883-021-02396-1. Abstract retrieved through Europe PMC, https://europepmc.org/article/MED/34856949 Accessed 3 August 2026.
  21. Busari N. Selma Blair’s documentary gives MS the visibility it needs. MS Society (UK) community blog, 25 October 2021. https://www.mssociety.org.uk/support-and-community/community-blog/selma-blairs-documentary-gives-ms-visibility-it-needs Accessed 3 August 2026.
  22. National Library of Medicine, Clinical Table Search Service. ICD-10-CM codes for multiple sclerosis: G35.A, G35.B0 to G35.B2, G35.C0 to G35.C2 and G35.D. https://clinicaltables.nlm.nih.gov/apidoc/icd10cm/v3/doc.html Accessed 3 August 2026.

Review information

Written by: trialport editorial team
Reviewed by: Keith Berelowitz, Founder and CEO, trialport
Reviewed on: 3 August 2026
Next review due: 3 August 2027
References last checked: 3 August 2026

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