What Causes Multiple Sclerosis and Why Are Women at Risk? The Science Behind the Gap

Multiple sclerosis (MS) is one of those conditions that raises more questions than it answers. It’s chronic, unpredictable, and affects nearly 1 million people in the U.S. today, according to the National Multiple Sclerosis Society. One of the most striking things about MS? Women are diagnosed with it at least 2 to 3 times more often than men.

But why? What is it about MS that makes it so much more common in women? And what actually causes it in the first place?

Let’s break down what science currently knows about MS, where women’s higher risk comes in, and how ongoing research is uncovering new answers.

What actually is multiple sclerosis?

Multiple sclerosis is an autoimmune condition, meaning the body’s own immune system mistakenly attacks healthy tissue. In MS, the immune system targets the myelin sheath, which is the protective covering around nerves in the brain and spinal cord. Think of myelin like the insulation around an electrical wire. When that insulation is damaged, the electrical signals don’t travel as smoothly.

This disruption is what causes MS symptoms, which can vary widely from person to person. Some of the most common include:

• Numbness or tingling
• Fatigue that doesn’t go away with rest
• Muscle weakness or spasms
• Trouble with balance or walking
• Vision problems
• Cognitive changes, like brain fog or difficulty concentrating

But it’s worth remembering that MS is highly individual: no two people have the exact same experience. Symptoms can come and go (known as relapses and remissions), or they can gradually worsen over time.

MS symptoms in women

Women with MS often notice symptoms that feel a little different or show up at certain points in their lives because hormones play a real role in how MS behaves. Paying attention to these early clues can help you get answers sooner and start the treatment that supports you best.

Early signs of MS in women

The earliest signs of MS can be incredibly subtle, which is why so many women chalk them up to stress, tiredness, or simply having a lot on their plate. Still, little changes can be important. You might notice:

• Unexplained fatigue that sticks around no matter how much you rest and starts to get in the way of daily life
• Vision problems, often linked to optic neuritis, which can bring on blurred vision, eye pain, or temporary vision loss
• Numbness or tingling in your face, arms, legs, or fingers
• Balance issues or dizziness that seems to come out of nowhere
• Cognitive changes like trouble concentrating, forgetfulness, or that familiar feeling of brain fog
• Bladder problems or a sudden increase in urgency

Many women find that these symptoms appear, disappear, and circle back again, which makes it even harder to realise they are part of a bigger picture. If you are dealing with a mix of these signs and they keep returning, it’s worth bringing them up with a healthcare provider so you can get the clarity and support you deserve.

Symptoms of MS in women under 40

MS often shows up for the first time between ages 20 and 40, which makes this chapter of life an important one for paying attention to symptoms. Younger women may notice:

• Relapsing and remitting symptoms that flare for a while and then ease up
• Heat sensitivity where symptoms feel worse in hot weather or after a workout
• Sexual dysfunction or changes in sensation that feel out of the ordinary
• Mood changes like depression or anxiety, which can be part of MS itself or a reaction to what is happening

These signs can overlap with some of the busiest years of your life. Building a career, thinking about a family, juggling responsibilities, and trying to stay afloat can make it easy to blame everything on stress or exhaustion. That overlap often leads to delays in diagnosis, sometimes for years, so trust yourself if something feels off and keep advocating for answers.

Symptoms of MS in women over 40

Women diagnosed with MS after 40 often notice a different pattern compared to those diagnosed earlier in life. Some have been dealing with unexplained symptoms for years, while others start experiencing MS for the first time during perimenopause or menopause. In this stage of life, symptoms may include:

• Progressive symptoms that steadily get worse rather than showing up in clear relapses
• Increased mobility issues that make walking or coordination more challenging
• More noticeable cognitive changes that can be confused with early menopause symptoms
• Muscle stiffness and spasms that can be uncomfortable and difficult to ignore

Shifts in hormones during perimenopause and menopause can also influence MS activity. Some women find their symptoms intensify as estrogen levels drop, although researchers are still learning exactly how the two are connected.

What causes MS in women?

Here’s the tricky part: there isn’t one single cause of MS. Instead, researchers believe it’s a combination of factors: genetic, environmental, hormonal, and even viral. Women’s higher risk comes from the unique way these factors interact in female biology.

Genetics

Having a family history of MS slightly raises the risk, but it’s not as straightforward as inheriting one “MS gene.” Instead, there are over 200 genetic variations linked to MS risk, many of which are connected to how the immune system functions. A person may carry genetic factors that make their immune system more likely to misfire, but it usually takes other triggers to actually develop MS.

Environment

Where you live matters. MS is more common in areas farther from the equator, possibly because of lower vitamin D exposure from sunlight. Low vitamin D is known to affect immune function, and several studies suggest it may play a role in MS risk.

Smoking is another environmental risk factor, with research showing that smoking can both increase the risk of developing MS and make the disease progress more quickly.

Hormones

This is one of the biggest reasons women are more affected than men. Estrogen and progesterone (the main female sex hormones) have powerful effects on the immune system. Fluctuations in these hormones (such as during puberty, pregnancy, or menopause) seem to influence MS activity. For example, many people with MS notice fewer relapses during pregnancy, when estrogen levels are high, followed by a rebound in symptoms after giving birth.

Viral triggers

One of the most exciting developments in MS research came in 2022, when a landmark study from Harvard University and the U.S. military showed that infection with the Epstein-Barr virus (EBV) (the same virus that causes mono) may be a major trigger for MS. In fact, the study found that people who had EBV were 32 times more likely to develop MS than those who hadn’t been infected.

EBV doesn’t explain everything, but it’s a big piece of the puzzle. Scientists believe the virus may set off an abnormal immune response in genetically susceptible individuals, and women seem to be more vulnerable to this effect.

Why are women more at risk for MS?

It’s not just a coincidence that MS disproportionately affects women. The gender gap in MS is one of the largest among autoimmune diseases, and here’s why:

Immune system differences

Women’s immune systems tend to be more active than men’s, which is helpful when fighting infections but can also backfire, leading to a higher chance of autoimmune conditions like MS, lupus, and rheumatoid arthritis.

Hormonal changes

Hormonal shifts throughout life (puberty, menstrual cycles, pregnancy, and menopause) can all influence how MS develops or progresses. For example, symptoms may worsen during the postpartum period, likely because hormone levels drop quickly after delivery.

The X chromosome factor

Women have two X chromosomes, while men have one. Some immune-related genes are found on the X chromosome, and researchers suspect that having two copies may contribute to women’s increased susceptibility to MS.

Lifestyle and stress

It’s worth acknowledging that women are often disproportionately affected by stress, healthcare inequities, and social pressures, all of which can indirectly influence disease risk and management. While stress itself isn’t a direct cause of MS, chronic stress can affect immune function, which may contribute to disease activity.

Who gets MS? Risk factors to know

While MS can affect anyone, the following factors can increase the likelihood of developing it:

• Sex: Women are at least twice as likely as men to be diagnosed.
• Age: MS often begins between ages 20 and 40, but it can develop at any age.
• Geography: Living farther from the equator, where there’s less sunlight, is linked to higher MS rates.
• Family history: Having a parent or sibling with MS raises your risk.
• Certain infections: Past infection with EBV significantly increases MS risk.
• Lifestyle factors: Smoking, obesity, and low vitamin D levels are all associated with higher risk.

MS research is finally catching up to women’s reality

Multiple sclerosis is complex, with no single cause. Instead, it’s the result of a mix of genetics, environment, viral triggers, and hormonal influences. Women are more at risk because of their immune systems, hormone cycles, and genetic makeup.

The science is still evolving, but what’s clear is that women’s experiences with MS deserve focused research and care. If you’re concerned about symptoms, speaking with a neurologist is the first step. Early diagnosis and treatment can make a huge difference in how the condition progresses.

While there’s still no cure for MS, research is moving fast. The EBV discovery has opened doors for potential vaccines or antiviral treatments that could one day prevent MS altogether. New medications are also making it possible to slow disease progression and improve quality of life for people living with MS.

Knowledge, advocacy, and support are powerful tools, and they’re reshaping the future of MS care, especially for women.

Managing MS isn’t only about treating symptoms; it’s about finding a therapy that supports your lifestyle, too. With oral convenience and improved GI tolerability, learn more about how VUMERITY can keep you moving forward with confidence.