Multiple sclerosis (MS) is one of the most widespread disabling neurological conditions of young adults around the world.

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You can develop MS at any age, but most people receive diagnoses between 20 and 50 years old.

There are relapsing-remitting and progressive types of MS, but the course is rarely predictable. Researchers still don’t fully understand the cause of MS or why the rate of progression is so difficult to determine.

Many people living with MS do not develop severe disabilities. Most have an average or near-average lifespan.

There’s no national or global registry for new MS cases. Known figures are only estimates.

Recent findings from the National MS Society estimate that nearly 1 million people in the United States are living with MS. This is more than double the last reported number and the first national research on MS prevalence since 1975.

An estimated 2.5 million people live with MS worldwide. An estimated 200 new cases are diagnosed each week in the United States, according to the MS Discovery Forum.

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Rates of MS are usually higher further from the equator. Some researchers consider vitamin D deficiency as a possible explanation for this.

According to the National Institute of Neurological Disorders and Stroke (NINDS), people with relatively higher levels of vitamin D are less likely to develop MS. Those that do develop MS may be more likely to have a less severe case.

A 2019 estimate segmented the United States into four regions with the following prevalence:

  • Northeast: an estimated 377 cases per 100,000 people
  • Midwest: an estimated 353 cases per 100,000 people
  • South: an estimated 277 cases per 100,000 people
  • West: an estimated 277 cases 100,000 people

People of Northern European descent have the highest risk of developing MS, no matter where they live. Meanwhile, the lowest risk appears to be among people of Native American, African, and Asian descent.

Children can get MS, too. About 5,000 children and teens currently live with MS in the United States, and about 10,000 children live with it worldwide, according to the National MS Society.

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Sex is a risk factor for developing MS. MS is three times more common in females than males.

People with biological relatives who have MS also have a higher risk of developing the condition. Researchers estimate the heritability — or ability to inherit MS — to be between 35–75%. First-degree relatives of someone with MS have a 2.5–5% risk of developing MS.

MS is not an inherited disorder, though. But a genetic predisposition to MS may be inherited.

According to NINDS, potentially dozens to hundreds of variations among genes may combine to create a genetic predisposition to developing MS.

Children of parents with MS may have a 10 to 20 times greater chance of developing the condition than the general population. In the case of identical twins, if one twin has MS, there’s a 1 in 4 chance that the other twin will also have the disease.

Researchers and neurologists still can’t say with certainty what causes MS. The ultimate cause of MS is damage to myelin, nerve fibers, and neurons in the brain and spinal cord. Together these make up the central nervous system.

Researchers speculate that a combination of genetic and environmental factors is at play, but it’s still not fully understood how.

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The relationship between the immune system and the brain may be considered a culprit. Researchers suggest the immune system may mistake typical brain cells for foreign ones.

One thing the MS community knows for certain is that the disease is not contagious.

Clinically isolated syndrome (CIS)

CIS is considered to be one course of MS, but it may or may not progress to MS.

People who are at high risk of developing MS are found to have lesions on the brain that can be detected through magnetic resonance imaging (MRI). Those with brain lesions have a 60–80% chance of receiving an MS diagnosis within a few years, according to the National MS Society.

Meanwhile, people at low risk don’t have MRI-detected brain lesions. They have a 20% chance of receiving an MS diagnosis in the same amount of time.

Relapsing-remitting MS (RRMS)

RRMS is characterized by clearly defined relapses of increased disease activity and worsening symptoms. These are followed by remissions when the disease doesn’t progress.

Symptoms may improve or disappear during remission. Approximately 85% of people receive a diagnosis of RRMS at first, according to the National MS Society.

Secondary progressive MS (SPMS)

SPMS can follow an initial RRMS diagnosis. Disability may gradually increase as the disease progresses, with or without evidence of relapse or changes in an MRI scan. Occasional relapses may occur, as well as periods of stability.

Untreated, about 50% of people with RRMS transition to SPMS within a decade of the initial diagnosis. About 90% of people transition within 25 years.

Primary progressive MS (PPMS)

PPMS is diagnosed in about 15% of people with MS. People with PPMS experience a steady progression of the disease with no clear relapses or remissions. The rate of PPMS is equally divided between males and females.

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A high percentage of MS cases do not progress.

A small number — about 3% — of cases may fit into a designation of “benign MS” after 15 years. However, the prevalence and criteria for benign MS are considered controversial. This diagnosis is often based on the Expanded Disability Status Scale (EDSS), which measures MS disability.

But despite a lack of noticeable disability, people with benign MS may have ongoing CNS damage from the disease.

At the other end of the spectrum, a 2015 study suggests that 8% of people with MS develop a more aggressive course of the disease. It’s known as highly active relapsing-remitting multiple sclerosis (HARRMS).

Symptoms vary a great deal from one person to another. No two people have the same combination of symptoms. This, of course, complicates identification and diagnosis.

In a 2017 report by healthcare company Merck, one-fifth of European women surveyed received misdiagnoses before eventually receiving an MS diagnosis. The average woman in the report was found to go through about five visits with a healthcare professional over 6 months before reaching a diagnosis.

According to the MS Foundation, symptoms can affect the mind, body, and senses in several ways, including:

  • blurred or double vision, or total vision loss
  • hearing impairment
  • reduced sense of taste and smell
  • numbness, tingling, or burning in the limbs
  • loss of short-term memory
  • depression or personality changes
  • headaches
  • changes in speech
  • facial pain
  • Bell’s palsy
  • muscle spasms
  • difficulty swallowing
  • dizziness, loss of balance, or vertigo
  • incontinence or constipation
  • weakness and fatigue
  • tremors or seizures
  • erectile dysfunction or lack of sexual desire

There’s no single test for MS. To receive a diagnosis, a doctor needs to collect your medical history and perform a neurological examination and a series of other tests. Tests may include:

  • MRI
  • spinal fluid analysis
  • blood tests
  • evoked potentials (such as an EEG)

Since the exact cause of MS is still unknown, there’s no known prevention.

There’s no cure for MS yet, but treatments can help manage symptoms. MS medications are designed to lessen the frequency of relapses and slow the progression of the disease.

There are currently several disease-modifying medications approved by the Food and Drug Administration to treat MS. They include:

Injectable medications

  • beta interferons, such as interferon beta-1a (Avonex, Plegridy, Rebif) and interferon beta-1b (Betaseron, Extavia)
  • glatiramer acetate (Copaxone, Glatopa)
  • ofatumumab (Kesimpta)

Oral medications

  • teriflunomide (Aubagio)
  • monomethyl fumarate (Bafiertam)
  • dimethyl fumarate (Tecfidera)
  • fingolimod (Gilenya)
  • cladribine (Mavenclad)
  • siponimod (Mayzent)
  • ponesimod (Ponvory)
  • diroximel fumarate (Vumerity)
  • ozanimod (Zeposia)

Infused medications

  • alemtuzumab (Lemtrada)
  • mitoxantrone (Novantrone)
  • ocrelizumab (Ocrevus)
  • natalizumab (Tysabri)


These medications are not approved for use during pregnancy. It’s also unclear if MS medications are excreted through breast milk. Talk with a doctor about your MS medications if you’re considering becoming pregnant.

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People with MS can safely carry a baby to term. Pregnancy doesn’t generally affect MS in the long term.

MS has been found to affect decisions about pregnancy, though. In the 2017 Merck report, 36% of women surveyed decided not to have children at all or postponed the timing of getting pregnant due to their MS.

People with MS often experience relief from symptoms during pregnancy, and breastfeeding after childbirth may reduce the risk of a relapse, according to the National MS Society.

MS is an expensive disease to treat. A 2016 economic analysis of MS found the total lifetime costs per person with MS to be $4.1 million. The average yearly healthcare costs range from $30,000 to $100,000 based on the mildness or severity of the disease.