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Memory problems, reduced concentration, a sense of slowed thinking and difficulty handling several tasks at once are common in multiple sclerosis. These symptoms may be direct manifestations of the disease, but cognitive performance is also influenced by depression, fatigue, sleep disorders, anxiety, pain and some medications.
For this reason, the complaint “my memory has become worse” in MS should not automatically be attributed either to multiple sclerosis itself or to depression. It is necessary to determine which cognitive functions have changed, how much this affects everyday life, and which potentially reversible factors contribute to the problem.
Cognitive changes are among the common manifestations of MS. In a meta-analysis of 90 studies, the pooled prevalence of objectively detected cognitive impairment was about 41%.
Estimates vary depending on the definition used. When cognitive impairment is defined strictly — for example, as reduced performance in at least two cognitive domains — prevalence may be lower. In a separate meta-analysis of people with relapsing-remitting MS, the estimate was about 33%.
Cognitive impairment is more common and usually more pronounced in progressive forms of MS, but it may already be present early in the disease and in people with relatively little physical disability.
Depression is also much more common than in the general population. In a large UK study of more than 5,600 people with MS, depression was identified in about 25%. Importantly, many patients were either untreated or continued to have substantial symptoms despite treatment.
Cognitive impairment and depression are often called “invisible symptoms” of MS. A patient may walk normally and have a low EDSS score, yet experience major difficulties at work because of slowed information processing or reduced concentration.
The cognitive profile of MS differs from classical dementia. In most patients, the issue is not a global loss of intelligence or memory, but a more selective disturbance of specific functions.
One of the functions most sensitive to MS. The person needs more time to take in information, compare it with what is already known and produce a response.
It may become harder to sustain attention, switch rapidly between tasks or work effectively when there are external distractions.
There may be difficulty holding information temporarily while using it for an ongoing task — for example, remembering several steps of an instruction while carrying them out.
Learning new material may become slower. Sometimes more repetitions are needed, while information that has already been well learned remains relatively preserved.
Planning, organizing a sequence of actions, monitoring errors, solving complex problems and changing strategy quickly may become more difficult.
Some patients have difficulty remembering and analyzing visual information, especially when spatial demands are complex.
Vocabulary, long-established knowledge and general intellectual ability often remain relatively preserved even when information processing speed is clearly reduced.
Patients often describe cognitive change with one word — “memory”. In reality, several different mechanisms may lie behind this complaint.
To remember new information, a person first has to notice it, process it quickly enough and sustain attention. If information processing is slowed or attention is easily exhausted, the material may never be encoded efficiently in the first place. Later, this is experienced as forgetfulness.
For example, someone may remember material well after reading it calmly several times, but have difficulty recalling the content of a fast-paced work meeting where listening, analyzing and preparing a response all happen at once.
A patient may remember an event after a cue or recognize the correct answer among several options, but retrieve it less effectively without prompting. This differs from the marked impairment of memory formation and storage seen in some neurodegenerative disorders.
This distinction is not absolute, but it helps explain why a general complaint about memory requires a more precise assessment of the cognitive profile.
Cognitive impairment in MS is not linked to one single lesion. It reflects injury to distributed neural networks throughout the brain.
The most important mechanisms include:
Two patients with a similar number of T2 lesions can therefore have very different cognitive performance. What matters is not only lesion count, but also lesion location, gray-matter damage, the degree of atrophy and preservation of functional connectivity between brain regions.
An important role is played by cognitive reserve — the brain’s ability to compensate for structural damage by using preserved neural networks more efficiently.
Cognitive reserve is influenced by education, professional and intellectual activity, the complexity of everyday cognitive tasks, physical activity and other factors. It does not prevent lesions from forming, but may partly determine how quickly structural injury becomes functionally apparent.
Depression in MS should not be viewed solely as a psychological reaction to chronic illness.
Uncertainty about the future, work limitations, fatigue, pain, sexual dysfunction and changes in social roles can certainly contribute to depression. At the same time, biological mechanisms are also discussed, including altered neural-network function, chronic inflammation and structural brain changes.
Common features of depression include:
Fatigue and sleep disturbance are also common in MS itself, so depression cannot be diagnosed from these symptoms alone. The overall clinical picture is what matters.
The relationship between depression and cognition in MS is bidirectional and clinically important.
A meta-analysis found that more severe depressive symptoms were associated with poorer performance across several cognitive domains. The strongest associations were seen with information processing speed, attention, overall cognitive efficiency and working memory.
Depression can worsen cognitive performance in several ways: it can reduce sustained attention, slow decision-making, lower motivation, disrupt sleep and increase subjective fatigue.
At the same time, the presence of depression does not mean that every poor cognitive test result should be explained by depression. Objective slowing of information processing or memory impairment may persist after successful treatment of depression because these deficits may also have an independent neurological basis.
In practice, when depression and cognitive complaints coexist, both should be addressed. Treating depression can improve concentration and subjective memory, but marked objective cognitive impairment still requires its own assessment.
Cognitive performance in MS depends strongly on the person’s overall functional state.
Fatigue may appear not only as physical exhaustion but also as reduced ability to sustain mental effort. A patient may perform well at the beginning of a task, but after 20–30 minutes make more errors or become substantially slower.
This type of cognitive fatigability should be distinguished from a persistent cognitive deficit.
Sleep deprivation, insomnia, restless legs syndrome, nocturnal spasms, frequent urination and obstructive sleep apnea may all worsen attention, information processing speed and daytime performance.
A 2024 systematic review confirmed an association between sleep problems and cognitive outcomes in MS, although the strength of the relationship varied depending on how sleep and cognition were measured.
Marked anxiety can also impair concentration. A substantial share of cognitive resources may be consumed by constant threat monitoring, doubt and repetitive rumination.
When anxiety, depression and fatigue coexist, the patient may subjectively experience a dramatic decline in memory even when objective cognitive impairment is relatively mild.
Apathy is characterized by reduced initiative and spontaneous activity. A person may start fewer activities independently and require more external prompting, while not necessarily feeling persistent sadness, guilt or hopelessness.
Apathy can coexist with depression, but the two are not identical.
Some patients with neurological disease have involuntary episodes of crying or laughing that are disproportionate to their actual emotional state. This is called pseudobulbar affect.
Frequent crying in this situation does not necessarily indicate depression. The key difference is the mismatch between the outward emotional expression and the person’s internal mood.
A diagnosis of MS does not exclude other causes of worsening memory or concentration.
Depending on the situation, clinicians may need to consider:
Some medications may increase sleepiness, slow reaction time or worsen attention. This can occur, for example, with strongly sedating or anticholinergic drugs, benzodiazepines, and some treatments for neuropathic pain, spasticity or bladder dysfunction.
This does not mean that such medications should simply be stopped. Dose, timing, clinical necessity and possible alternatives should be reviewed.
Assessment begins not with a test, but with clarification of the complaint itself.
It is important to understand:
The patient’s complaint is important, but subjective severity does not always match objective testing. Depression, anxiety and fatigue have a particularly strong effect on subjective cognitive complaints.
For brief cognitive screening in MS, the most widely used tool is the Symbol Digit Modalities Test (SDMT).
The patient is shown a key in which symbols correspond to specific numbers, and then must match symbols with the correct numbers as quickly as possible.
The main outcome is the number of correct responses within a limited time. The test primarily measures information processing speed, but also requires attention, visual scanning and working memory.
SDMT is sensitive to cognitive change in MS and convenient for repeated follow-up. Interpretation should take into account age, education, language, vision, motor function and practice effects from repeated testing.
When a broader but still relatively brief assessment is needed, clinicians can use the Brief International Cognitive Assessment for Multiple Sclerosis (BICAMS).
It contains three components:
BICAMS does not replace a full neuropsychological evaluation, but it allows assessment of three of the cognitive domains most vulnerable in MS within a relatively short time.
The Montreal Cognitive Assessment (MoCA) and Mini-Mental State Examination (MMSE) were designed for broader screening of cognitive impairment.
They can be useful in selected situations, especially when a more global cognitive disorder needs to be excluded, but a normal MoCA or MMSE does not exclude the typical cognitive deficits seen in MS.
It is particularly useful when:
Standardized questionnaires are used for initial screening. Common examples include the Hospital Anxiety and Depression Scale (HADS) and the Patient Health Questionnaire-9 (PHQ-9).
A questionnaire does not establish a final psychiatric diagnosis. A positive screen means that clinical assessment is needed.
In MS, symptom overlap is especially important. Fatigue, poor sleep and reduced performance may reflect either depression or the neurological disease itself. Persistent low mood, anhedonia, hopelessness, marked loss of self-esteem and suicidal thoughts are therefore particularly important diagnostically.
Standard MRI is essential for assessing disease activity and the overall pattern of CNS involvement in MS, but an ordinary scan cannot accurately predict an individual patient’s cognitive status.
Cognitive impairment is associated with:
In a 2024 systematic review and meta-analysis, thalamic volume was among the MRI measures most consistently associated with performance across different cognitive tests.
The number of T2 lesions alone does not determine a patient’s intelligence or memory. MRI and cognitive testing answer different questions and complement each other.
Neurofilament light chain (NfL) is a marker of ongoing neuroaxonal injury, while glial fibrillary acidic protein (GFAP) mainly reflects astroglial pathology and is of particular interest in progressive MS.
These markers may complement clinical and MRI assessment of disease activity, but neither NfL nor GFAP is a test of memory or cognitive function.
An elevated NfL value cannot prove that a specific complaint is caused by cognitive worsening, and a normal result does not exclude cognitive impairment.
Disease-modifying therapies (DMTs) are primarily intended to control pathological immune activity and reduce the risk of new CNS injury.
Preventing new inflammatory lesions and neuroaxonal damage can reasonably be viewed as a way to preserve cognitive reserve. In clinical trials of several DMTs, more favorable trajectories in some cognitive measures have indeed been reported.
However, cognitive endpoints have not been used consistently across drug trials, so direct comparison of different DMTs by their ability to preserve memory or processing speed is difficult.
No DMT is approved specifically for the treatment of cognitive impairment.
An isolated subjective memory complaint or a single low result on one test is usually not enough to justify switching DMT. If objective cognitive decline occurs together with other signs of disease activity or progression, it becomes part of the overall clinical assessment.
Treatment starts by looking for factors that can be changed. In one patient the main contributor may be MS activity, in another depression, and in another chronic sleep deprivation — often several causes coexist.
The first priority is to prevent new nervous-system injury with appropriate disease-modifying therapy.
Cognitive rehabilitation includes training impaired functions and learning strategies that help compensate for persistent deficits.
Systematic reviews and meta-analyses show moderate benefit, although effects differ across methods and cognitive domains. There is no single computer program that improves memory, attention and executive functions equally well in every patient.
The most rational approach is individualized rehabilitation based on the patient’s specific cognitive profile.
If information processing speed cannot be fully restored, its impact on daily life can still be reduced. External reminders, calendars, structured task lists, written instructions, reducing multitasking and organizing the work environment can all help.
Physical activity is beneficial not only for walking and general endurance. Current evidence suggests a moderate positive effect on some cognitive outcomes, especially information processing speed.
This does not mean that exercise replaces cognitive rehabilitation, but it is an important component of a comprehensive approach.
Chronic insomnia, excessive daytime sleepiness, loud snoring or suspected sleep apnea should be investigated and treated. Improving sleep can substantially improve daytime cognitive performance even if the MS itself is unchanged.
Depression in MS should be treated as seriously as motor or sensory symptoms. It affects quality of life, work ability, adherence to therapy and the perception of other symptoms.
The strongest MS-specific evidence is available for cognitive behavioural therapy (CBT).
A meta-analysis of 15 randomized trials involving more than 1,500 patients found a moderate reduction in depressive symptoms and a smaller but statistically significant effect on anxiety.
Therapy can be delivered in person or remotely, individually or in groups. The key issue is not the format itself, but a structured program and adequate professional expertise.
Medication may be needed for moderate or severe depression, recurrent episodes or insufficient response to psychotherapy.
Direct comparative evidence for antidepressants specifically in MS is much weaker than in general psychiatric practice. Medication is therefore selected according to general principles of depression treatment, while taking the individual patient’s clinical situation into account.
Factors considered include:
Excessive sedation or anticholinergic effects can further worsen daytime concentration, so cognitive complaints should also be considered when choosing therapy.
Regular physical activity can also improve depressive symptoms and should be part of a comprehensive treatment plan, but clinically significant depression may still require psychotherapy and/or medication.
Some difficulties can be reduced by changing how everyday work is organized.
These strategies are not a “treatment for memory”, but they can substantially reduce the functional impact of cognitive deficits.
The potential for improvement depends on the cause of the impairment.
If a substantial part of the problem is related to depression, insomnia, medication adverse effects or marked fatigue, correcting these factors can produce a noticeable improvement.
After a relapse, some cognitive functions may partly recover as inflammation subsides and through neuroplasticity.
When persistent structural damage is present, the goal is often not complete return to the previous level, but a combination of disease stabilization, training of preserved functions and effective compensation for residual deficits.
For this reason, saying that “cognitive impairment in MS is untreatable” is just as inaccurate as promising to “fully restore memory”. The realistic prognosis depends on the cause, severity and course of the disorder.
Typical cognitive impairment in MS usually develops gradually. Sudden confusion, marked disorientation or abrupt behavioral change should not automatically be attributed to multiple sclerosis.
Urgent assessment is needed for:
Suicidal thoughts should not be considered a “normal reaction to chronic illness”. If there is a specific plan, intent to self-harm, or an inability to remain safe, immediate medical or psychiatric help is required.
Objective cognitive impairment is found in about 40% of patients, although frequency depends on disease stage and the method used. The most typical change is not isolated memory loss, but slower information processing and reduced efficiency of learning new material.
No. The typical cognitive profile in MS differs substantially from classical dementias. Processing speed, attention and learning are more often affected, while long-established knowledge and general intellectual ability may remain preserved. Marked global cognitive decline requires investigation for other causes.
Yes. Depression can reduce attention, motivation, processing speed and working memory. However, depression does not exclude a simultaneous objective cognitive deficit related to MS.
The Symbol Digit Modalities Test (SDMT) is the most widely used brief screening tool. It is very sensitive to slowing of information processing. For a broader short assessment, BICAMS can be used.
No. MoCA was not designed specifically for the typical cognitive profile of MS and may miss mild or isolated slowing of information processing. More MS-specific testing may still be appropriate when complaints are present.
MRI shows structural brain injury but does not measure cognition directly. Thalamic atrophy, global brain atrophy, gray-matter damage and higher lesion burden are associated with poorer cognitive performance, but memory or attention cannot be determined precisely from MRI alone.
No medication has convincing evidence and approval specifically for cognitive impairment in MS. Management focuses on control of disease activity, treatment of depression, sleep and other reversible factors, physical activity and cognitive rehabilitation.
Some cognitive rehabilitation programs are beneficial, but results vary by method and cognitive domain. Simply doing large numbers of “brain games” does not guarantee that improvement will transfer to real-world tasks.
Yes. Current evidence suggests a moderate positive effect of regular exercise on some cognitive measures, especially information processing speed. Physical activity also improves mood, sleep and overall functional capacity.
Yes. Depression has an important effect on quality of life and cognitive performance regardless of why it developed. Treating depression is an independent part of MS care and may also reduce the severity of cognitive complaints.
Objective cognitive assessment is especially useful if it has become harder to perform familiar professional work, handle large amounts of information, switch quickly between tasks, remember new instructions, or if relatives notice a persistent change in cognitive performance.
When these complaints coexist with depression, marked fatigue or sleep disturbance, it is important to determine the contribution of each factor rather than explain everything by one cause.
Consult Dr. Lidiia PrakhovaThis page reflects the state of clinical evidence as of September 2026 and is intended for educational purposes. Results of brief cognitive tests and depression questionnaires should be interpreted in the clinical context and do not replace a full neurological or neuropsychological assessment.