Brain fog: symptoms, causes and support
Brain fog can make everyday life very difficult. What causes this cognitive impairment, what can help – and when it makes sense to seek professional advice.
Key points in brief
- Brain fog describes a state of mental sluggishness, difficulty concentrating and mental exhaustion.
- Typical symptoms include drowsiness, forgetfulness, difficulty finding the right words and feeling quickly overwhelmed by everyday tasks.
- Common causes range from stress, lack of sleep, infections such as long COVID and hormonal changes to nutritional deficiencies, mental health conditions, neurological disorders and medication.
- Brain fog is usually temporary. Lifestyle factors such as sleep, exercise, hydration, stress reduction and a clear daily routine can play an important role in recovery.
- It is important to seek medical advice if symptoms persist for weeks, worsen or are accompanied by warning signs such as paralysis, vision problems or speech difficulties.
Almost everyone goes through periods when it is hard to think clearly. With brain fog, however, this feeling is more pronounced. Those affected feel mentally sluggish, unfocused, forgetful or unusually exhausted. But when does brain fog occur, how long does it last – and how can you tell that there isn’t something more serious behind it?
What is brain fog?
Brain fog doesn’t usually mean that the brain is damaged or that dementia is developing. It is often caused by a temporary decline in mental resilience. The term is used to describe a range of cognitive difficulties.
Brain Fog has become widely known among the general public, particularly since the COVID-19 pandemic. Many people affected by long COVID have reported mental exhaustion, difficulty concentrating and a significant reduction in mental performance.
“Brain fog is when you can’t think clearly or focus well. It feels as if your mind is stuck in a thick, slow-moving liquid.”
What are the typical symptoms of brain fog?
“Brain fog is not a clearly defined clinical condition, but rather a symptom,” explains Dr Lara Diem, senior physician at the Neuroscience Centre of the Lucerne Cantonal Hospital. “Those affected feel mentally sluggish, unable to concentrate, or simply as if they are in a fog.”
Common symptoms of brain fog include:
- A feeling of dizziness or a foggy head
- Difficulty concentrating
- Forgetfulness
- Difficulty finding words
- Slowed thinking
- Difficulty absorbing or processing information
- Difficulty making decisions
- Mental exhaustion
- Quickly becoming overwhelmed by complex tasks
- Difficulties with planning or organising
- Difficulty following conversations
Distinguishing brain fog from a serious illness
Brain fog differs from dementia primarily in terms of how it develops. Dementia usually develops slowly and progressively. Mood and personality can also change gradually.
If your memory and concentration are starting to slip, it could also be a sign of burnout. These symptoms are associated with chronic, unresolved work-related stress.
“Brain fog is usually harmless and temporary – for example, due to lack of sleep or stress,” says Dr Diem. “You need to take a closer look if the symptoms persist for weeks, worsen and are accompanied by neurological symptoms such as paralysis, vision problems or speech difficulties.”
“The causes are varied and often overlap.”
What are some common causes?
There is no single explanation for brain fog. It usually occurs when several stress factors come together. “The causes are indeed varied and often overlap,” adds Diem. Lara Diem explains:
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Infections/long COVID
“After viral infections – especially COVID-19 – many people report ongoing cognitive problems. Studies show that a significant proportion of patients are affected weeks to months after infection.”
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Hormonal changes
“During menopause or pregnancy, hormonal fluctuations can lead to difficulty concentrating. This happens often, but it is usually temporary.”
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Stress
“Chronic stress is one of the most common causes,” says Dr Diem. “It leads to chronic overstimulation of the nervous system and impairs attention and memory.”
A concerning finding: one in four people in Switzerland feels stressed, according to a study in the Sanitas Health Forecast 2025. Younger people and women are particularly affected.
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Deficiencies
Lara Diem explains that brain fog can also occur when the body is lacking something essential. In many cases, lack of sleep plays a role. People who consistently get too little sleep or poor-quality sleep are less alert during the day, more forgetful and tire more easily.
A lack of exercise and not drinking enough fluids can also contribute to that fuzzy, foggy feeling in your head.
Although less common, it is important to rule out a vitamin B12 deficiency – especially in people who follow a vegan diet, the elderly or people with certain gastrointestinal conditions.
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Illness
Brain fog can also occur in connection with certain medical conditions. Depression and anxiety often play a role because they impair concentration, memory and mental resilience.
In ADHD, attention problems usually begin in childhood but often become more apparent in adulthood when under stress.
Metabolic disorders such as diabetes or autoimmune diseases can also cause brain fog.
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Neurological disorders
“Neurological disorders can also be associated with brain fog. Fatigue combined with cognitive impairment is one of the most common symptoms, particularly in multiple sclerosis – often regardless of visible relapses,” says the neurologist.
Other possible causes include inflammatory disorders of the nervous system and, in rare cases, neurodegenerative diseases.
“It is important to note that in these cases, there are usually additional symptoms, such as sensory disturbances, visual disturbances or unsteadiness when walking, which is why a medical evaluation is crucial.”
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Medication
Some medicines and treatments can cause cognitive side effects.
These include, for example, chemotherapy, certain psychiatric medications such as antidepressants, sleeping pills, strong painkillers and some allergy medications. They can impair concentration, memory, or reaction time.
Why do infections, stress or hormonal changes trigger similar symptoms?
“Many of these factors affect the same systems in the brain,” explains Diem. These include neurotransmitters such as dopamine and serotonin, which help regulate attention, motivation and mood.
Inflammatory processes can disrupt communication between nerve cells, making it harder to think, remember and concentrate. The brain is not switched off, but it works less efficiently – like a network with a poor connection.
What can I do to combat brain fog?
Treatment depends on the cause. However, according to neurologist Lara Diem, there are some proven basic principles:
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Optimise the foundation
- Regular and consistent sleep
- Drink plenty of water
- Light, regular exercise
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Energy management (pacing)
- Schedule activities
- Avoid overload
- Plan breaks strategically
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Reduce stress
- Relaxation techniques, such as breathing exercises or meditation
- Structured daily routine
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Cognitive strategies
- Break tasks into smaller steps
- Use notes and routines (lists, calendar)
- Avoid multitasking
- Memory training
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Brain retraining programmes
- These are programmes designed to regulate the nervous system’s response to stress and stimuli. They use the brain’s neuroplasticity through targeted mental exercises.
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Medical treatment (if necessary)
- Treatment of depression, anxiety or ADHD
- Substitution in cases of deficiency
- Individualised therapeutic trials for fatigue syndromes in consultation with a doctor
“Important: Brain fog itself does not cause structural damage to the brain.”
Are there any known long-term effects of brain fog?
Dr Diem explains: “Whether brain fog lasts longer depends mainly on the cause.” In cases of stress or lack of sleep, the symptoms usually go away once the body has recovered.
In the case of long COVID or chronic fatigue syndrome, however, these symptoms can persist for months or even years. Improvement is also possible in psychiatric disorders if the underlying disease is treated.
“Important: Brain fog itself does not lead to structural damage to the brain,” Diem emphasizes. “But it can significantly impair quality of life.”
Warning signs: when should I see a doctor?
You should see a doctor if brain fog persists for a long time, gets worse or significantly interferes with your daily life. Any additional neurological symptoms, such as vision or speech problems, paralysis, numbness, unsteadiness, severe confusion, or unusually severe headaches, should be evaluated immediately.
How is brain fog diagnosed?
“Often, after the examination, patients find that their blood test results and other values are normal – and then feel that they aren’t being taken seriously,” said Diem. In reality, however, normal test results don’t mean that the symptoms aren’t real. Instead, they may be caused by functional or systemic factors.
Since there is no single test for brain fog, the diagnosis is made step by step:
- Consultation (medical history): When did the symptoms start? Are there any triggers, such as infections, stress or medication?
- Clinical examination: rule out neurological abnormalities
- Basic diagnostic tests: blood tests (e.g. inflammation markers, thyroid function, vitamin B12)
- Depending on the situation: Neuropsychological tests, imaging (MRI), sleep studies (sleep-wake disorders)
Conclusion
Brain fog isn’t all in your head, and it can have many causes – ranging from lack of sleep and stress to infections, medication or nutritional deficiencies. The good news is that symptoms often improve once triggers are identified and treated.
Regular sleep, staying hydrated, exercising, taking breaks, reducing stress and having a structured daily routine can also help reduce the strain on the brain.
However, if symptoms persist for weeks, worsen or are accompanied by neurological symptoms such as paralysis, vision problems or speech difficulties, you should consult a doctor.
