How Multiple Sclerosis Affects the Brain

Cognitive impairment is common in people with multiple sclerosis (MS), with recent studies suggesting that it can affect anywhere from 32% to 65% of people with MS. Cognitive impairment can affect our ability to think, remember, learn and solve problems.

The brain lesions that are the hallmarks of MS most frequently affect processing speed, the learning or acquisition process of memory, and executive functioning, said Michael R. Mèager, PsyD, a clinical neuropsychologist and the founding director of Grey Matter Neuropsychology of New York.

“In MS, the development of lesions tends to be in the white matter—considered to be the cognitive highways responsible for information transmission,” Dr. Mèager said. The white matter in our brains are the nerve fibers that are protected by myelin sheaths. This is the part of the brain that exchanges information and communication.

The gray matter can also be affected, but to a lesser extent, Dr. Mèager said. The gray matter is the home for how we perceive, move, talk and learn. The role of the white matter is to send messages between different areas of gray matter.

“MS lesions (demyelination), and subsequent inflammation and scarring, cause the disruption and slowing of brain processes,” Dr. Mèager said. “Lesion location and their number may determine the level of cognitive impairment a person experiences.”

However, experts agree that there are many variables at play when it comes to MS and cognitive troubles.

Leigh Charvet, PhD, a clinical neuropsychologist at New York University (NYU) Langone Medical Center and professor in the Department of Neurology at NYU Grossman School of Medicine, said she often sees patients who are in a panic about losing cognitive functioning. She wants them to know that first of all, in most cases, cognitive effects tend to be mild, especially in younger people. Most importantly, they have some control over them.

“Sleep deprivation, medication side effects, cannabis and alcohol use, depression and anxiety, and just life can amplify mild cognitive slowing,” Dr. Charvet said. “What we tend to attribute to MS disease pathology is probably a combination of factors, many of which are modifiable.”

Here’s what to know about the factors that can play a role in cognitive problems and what you can do to stay sharp:

Physical Activity

Exercise is known to be cognitively preserving, with more and more data coming out to support that. Cardiovascular (aerobic) exercise, in particular, increases blood flow to the brain and decreases inflammation—a known culprit in neurodegenerative diseases like MS.

The U.S. Department of Health and Human Services’ Physical Activity Guidelines for Americans recommend that adults get at least 2 1/2 hours of moderate-intensity physical activity a week, if possible—but any amount is beneficial.

Diet

Scientists have yet to establish that any particular diet helps improve cognition in MS, but it’s known that eating a lot of sugar, red meat and processed foods can contribute to inflammation, so transitioning to a diet that focuses on whole grains, vegetables, fruit and lean poultry and fish is recommended. The MIND diet—which stands for Mediterranean-Dietary Approaches to Stop Hypertension (DASH) Intervention for Neurodegenerative Delay—is designed to improve brain health. One 2024 study found that, after adjusting for demographic and other factors, participants who adhered closely to the MIND diet had a 4% reduced risk of cognitive impairment compared to those with lowest adherence.

“A healthy diet and exercise should not be optional for optimal health and for cognitive preservation,” Dr. Charvet said.

Sleep

Getting a good night’s sleep—ideally 6 to 8 1/2 hours a night—is often a challenge for people with MS. Pain, stress, depression and medications can all disrupt sleep.

“If a person has poor sleep hygiene or an irregular sleep schedule, that’s going to exacerbate fatigue and also exacerbate cognitive symptoms,” Dr. Mèager said. “Someone without any disease burden who doesn’t get enough sleep or good quality sleep can feel that they’re running on fumes, and their cognitive abilities will not be as sharp as they could be. Imagine now having MS with sleep disturbances; you’re going to feel like your cognitive symptoms are further declining when it’s actually this moderator effect of sleep.”

Addressing sleep issues—whether through lifestyle changes, medication or cognitive-behavioral therapy—may go a long way toward improving memory and cognitive function.

Cannabis Use

In Dr. Charvet’s experience, cannabis use is prevalent in MS patients. “I’ve had patients seek it out, thinking it’s a healthy alternative to gabapentin or good for stress relief,” she said. “There’s no evidence that cannabis helps anything in MS other than certain cases of spasticity in people with advanced disease.” However, she said, “there is evidence that if people go off of cannabis, they have improved cognitive functioning and reduced depression.”

Medications

Drugs used to manage MS symptoms may have negative effects on cognition. That includes some medications used to treat depression and anxiety, if those are present. Gabapentin, commonly used to treat nerve pain and spasticity, may have side effects like fatigue, which then affects cognition.

Dr. Charvet recommended a thorough medication review with your doctor if you’re noticing cognitive effects. “People sometimes don’t realize that those drugs are not treating their disease; they’re managing their symptoms, sometimes very bluntly. There are specific drugs [that can be] cognitively impairing, and then just the overall drug burden is cognitively impairing.”

Depression and Anxiety

Chronic stress and depression, both common in MS, can lead to increased inflammation and elevated cortisol levels, which can negatively affect brain structures involved in memory and executive function, such as the hippocampus and prefrontal cortex.

Managing stress and depression through psychotherapy, mindfulness, medication and lifestyle changes may help protect cognitive function and improve overall quality of life for people with MS.

In addition to addressing modifiable factors, doing puzzles and learning new things (like a language or hobby) can help. Also beneficial to many MS patients is a more formal cognitive rehabilitation—or “brain training.” This is an intervention provided by neuropsychologists or rehabilitation psychologists that focuses on specific activities designed to improve attention, working memory, problem-solving and other cognitive skills. Cognitive rehabilitation has been proven to keep your mind active, improve cognitive skill and potentially delay further cognitive issues.