What Causes Cognitive Dysfunction?

Everyone living with MS knows that mobility challenges are just a small part of the challenges we face, even though they tend to get the most publicity. Multiple sclerosis also causes many invisible symptoms that many of us are all too familiar with including (but certainly not limited to) difficulty thinking, or cognitive dysfunction.

Our identities are often defined by our cognition

Our identities are often defined by our cognition. Cognition is the way we think, create, make plans, solve problems, make decisions, learn new things, and make memories. Fatigue and cognitive issues, not physical disability, are the biggest predictors of whether someone with MS will be able to continue working, or function independently at home. We can give you assistive devices to overcome your mobility challenges, but it is much more difficult to maintain employment or be a parent if you have difficulty multi-tasking or with retaining new information. Cognitive symptoms are particularly tricky to identify and treat because they may present differently in each person, and often the root cause of symptoms is complicated. That is why I teamed up with MultipleSclerosis.net to create this series, which will talk more about what cognition is, how we can better understand individual symptoms, and treatment options.

How MS affects cognition

Cognition is defined as our ability to think and perform. More than 65% of people with MS have difficulty with cognition during their lifetimes, making it one of the most common MS symptoms. The good news is that MS does not affect your overall intelligence, or long term memory. The most common cognitive symptoms in people living with MS include trouble with short term memory, attention, multi-tasking, word finding, and “executive functions” which include planning, prioritizing, and organizing. Cognitive decline generally occurs slowly over a long period of time, and while it is more common in progressive forms of MS, impairment can also occur at any point, including in the early stages of MS.

MS can directly impair cognition

MS can directly impair cognition in a few ways. During a relapse, or other extenuating circumstances (such as pain, illness, or being overheated) a sudden increase in fatigue and cognitive difficulties are common and even expected. When your body is in crisis mode your brain is distracted, and it has more difficulty thinking and performing normally. In these instances you should see your cognition improve as you recover, or get your pain under control. MS also causes the brain to atrophy, or shrink, at a faster rate which is associated with permanent cognitive dysfunction. It is difficult to track atrophy, but your neurologist will rely on your regular MRIs to show them whether you have significant atrophy. This is one reason why it is crucial to have regular MRIs to track your MS progression.

Other causes of cognitive dysfunction

While MS can directly lead to cognitive dysfunction, there are a lot of other factors to consider. In neurology we have a saying, “Treat the body right, and the mind will follow”. This basically means that when the body is struggling, the mind is too, and in MS we often see the consequences of this. When you are extremely fatigued, sick, sleep deprived, struggling to walk, or overheated it is very common to have cognitive symptoms at the same time. In those instances the brain is expending a lot of energy into a task that is normally second nature. If we find ways to help you manage fatigue, get better sleep, or preserve energy by using assistive mobility devices your brain will have more energy to think, and subsequently perform better. Sometimes just knowing that you have trouble doing a physical and cognitive task simultaneously (also called dual tasking), you can compensate. For instance, you can let your friend know that you would love to continue your lively conversation while sitting on that bench over there, because you are more likely to fall if you try to walk and talk at the same time.

Mental health

Mental health and cognition also go hand in hand. If a patient comes to me and says they have been struggling to remember things, the first thing I assess is their mood. Depression is one of the most common causes of cognitive dysfunction, and it is often overlooked because people do not realize they are depressed. We have been taught that depression means crying all the time, or feeling really blue. However, depression most often manifests as a disinterest in activities you used to enjoy, or a general lack of motivation. Anxiety also causes us to have trouble thinking through stressful situations, and can lead to trouble falling and/or staying asleep which leads to more fatigue and cognitive fogginess (often referred to as cog-fog). Treating depression and anxiety can significantly improve cognition, and a lot of my patients are shocked at what a difference it can make!


Medications can also either help or hurt cognition. Many of the medications that we use to control pain and muscle spasticity can make you tired, and worsen cog-fog. If your cognition seems to be worse than usual, mention it to your healthcare provider and see if your medications could be contributing. Often we can adjust dosages, or the timing of medications throughout the day to lessen the impact of side effects.

By providing your email address, you are agreeing to our privacy policy.

This article represents the opinions, thoughts, and experiences of the author; none of this content has been paid for by any advertiser. The MultipleSclerosis.net team does not recommend or endorse any products or treatments discussed herein. Learn more about how we maintain editorial integrity here.

Join the conversation

Please read our rules before commenting.