Anxiety & Mood
Brain fog: causes and what helps
Brain fog explained: what people mean by it, the most common causes, from sleep and anxiety to depression, ADHD and the thyroid, and what helps.
Brain fog describes slow, cloudy thinking: you find it hard to concentrate, you forget things, and simple tasks take effort. It is not a diagnosis. It is a description that fits many causes: too little sleep, anxiety, depression, ADHD, hormonal changes or physical illness. Treatment starts from the cause, so it is worth finding it.
What people mean when they say brain fog
Researchers at the University of Edinburgh read 717 Reddit posts that mentioned the term. In the 141 descriptions people gave of their own experience, the most common were:
forgetfulness (51 descriptions)
difficulty concentrating (43)
feeling disconnected, as if you are not fully “there” (34)
slow thinking and excessive effort (26)
difficulty communicating (22)
Half of the posts (363 of 717) were in groups about illnesses: COVID-19, psychiatric, neurodevelopmental, autoimmune and functional disorders. Several were about using or stopping substances and medicines. In plain words: the same word describes different experiences, with different causes.
What are the most common causes?
Too little sleep. In an analysis of 70 studies, total sleep deprivation of up to 48 hours worsened attention, working memory and speed of thinking. The largest effect was on “lapses” in simple attention.
Anxiety. In an analysis of 177 samples with 22,061 people, those who reported more anxiety did consistently worse on working memory tasks. In plain words: worry takes up space on the mind’s “notepad”, where we hold whatever we are thinking about at that moment.
Depression. A pooled analysis found moderate deficits in attention, memory and executive functions, that is, planning and organising. In attention and executive functions, the deficits remained even after mood improved. For other ways depression shows itself, see the article on depression symptoms in adults.
Perimenopause and menopause. Women in midlife often notice changes in thinking and memory as they go through the menopause. Many worry that it is the start of a more serious condition. The International Menopause Society notes that these changes are common and that doctors have a role in explaining them.
Hypothyroidism. A clearly underactive thyroid affects mood and thinking, and this improves to a large extent with treatment. Mild, “subclinical” hypothyroidism is not linked with major problems. If someone with mild hypothyroidism has severe psychological symptoms, there is probably another cause, which needs separate assessment.
After COVID-19. In a review of 81 studies, 12 weeks or more after diagnosis, 22% had cognitive difficulties and 32% had fatigue.
Substances and medicines. In the Edinburgh study, several posts linked the fog with using or stopping substances and medicines. If the fogginess started after a new medicine, or after stopping one, tell your doctor. Do not stop a medicine on your own.
Brain fog and ADHD
In ADHD, inattention and difficulty organising start in childhood. The European consensus statement on adult ADHD notes that it often continues throughout life and makes everyday life harder.
There is also a related set of symptoms that describes the “fog” almost word for word: excessive daydreaming, mental confusion and fogginess, slow movement and thinking. It used to be called “sluggish cognitive tempo”. An international group of experts recently proposed the name “cognitive disengagement syndrome” (CDS).
About 46% of adults with ADHD have raised levels of these symptoms, according to the epidemiological studies the group summarises.
The syndrome is also closely linked with depression.
It is not yet an official diagnosis. Researchers are debating whether it is a separate disorder, a form of ADHD or a feature that appears across many disorders.
A few studies suggest that ADHD medicines may improve these symptoms too.
In the assessment I distinguish “I can’t get started” from “I feel low”. The first is more suggestive of ADHD, the second of depression. When ADHD occurs together with severe anxiety or depression, I treat those first, because ADHD treatment can make them worse.
For how they differ, read the article ADHD or anxiety and depression?.
What the doctor will ask you
The “fog” does not show up on a single test. The cause is found mainly from your history:
when it started: in childhood or recently
how you sleep, and how much caffeine and alcohol you drink
whether your mood is low or anxiety is taking over
which medicines or substances you take, and whether anything changed recently
whether you recently had an infection and, for women, whether your cycle has changed
If needed, the doctor will ask for blood tests, for example for the thyroid.
When I find a physical cause, such as a thyroid disorder, we treat it first. It can mimic anxiety or ADHD and make them worse.
What helps
Treatment starts from the cause:
Sleep: if you sleep too little or irregularly, start there.
Anxiety or depression: treating them is the first step. In depression, thinking can be slow to recover, even when mood improves. Discuss this with your doctor.
ADHD: treatment is described in the article on adult ADHD treatment.
Hypothyroidism: treating it improves mood and thinking to a large extent.
Until the cause is found, you can try:
writing down whatever you do not want to forget, instead of holding it in your head
doing one task at a time and switching off notifications while you work
keeping a regular time for going to bed and waking up
Do not wait for your mind to “clear” before you start. When energy is low, action comes before mood: one small, specific step today.
When to ask for help
The fogginess lasts for weeks and makes work, study or relationships harder.
It comes with low mood, severe anxiety or insomnia.
Difficulties with concentration and organisation have been there since childhood.
It is gradually getting worse, or the people close to you notice that you forget more and more.
Safety: If, together with the fogginess, you suddenly have a drooping mouth on one side of the face, weakness in one arm, slurred speech, difficulty understanding what is said to you, loss of vision or a very severe headache, call 166 (ambulance, EKAV) or 112 immediately. It may be a stroke. If you have thoughts of harming yourself, call 166, 112 or the Suicide Prevention Line 1018.
How I can help
Book a psychiatric assessment, at the practice in Trikala or online. If you suspect ADHD, see the page on adult ADHD. If low mood dominates, see the page on depression treatment. The first conversation can also take place from your home: see how working with an online psychiatrist works, or book an appointment.
This article is educational and does not replace individual clinical assessment. Do not change or stop any treatment you are already taking without talking to your doctor.
Sources
McWhirter L, Smyth H, Hoeritzauer I, Couturier A, Stone J, Carson AJ. What is brain fog? J Neurol Neurosurg Psychiatry. 2023. https://doi.org/10.1136/jnnp-2022-329683
Lim J, Dinges DF. A meta-analysis of the impact of short-term sleep deprivation on cognitive variables. Psychol Bull. 2010. https://doi.org/10.1037/a0018883
Moran TP. Anxiety and working memory capacity: A meta-analysis and narrative review. Psychol Bull. 2016. https://doi.org/10.1037/bul0000051
Rock PL, Roiser JP, Riedel WJ, Blackwell AD. Cognitive impairment in depression: a systematic review and meta-analysis. Psychol Med. 2014. https://doi.org/10.1017/S0033291713002535
Maki PM, Jaff NG. Brain fog in menopause: a health-care professional’s guide for decision-making and counseling on cognition. Climacteric. 2022. https://doi.org/10.1080/13697137.2022.2122792
Samuels MH. Psychiatric and cognitive manifestations of hypothyroidism. Curr Opin Endocrinol Diabetes Obes. 2014. https://doi.org/10.1097/MED.0000000000000089
Ceban F, et al. Fatigue and cognitive impairment in Post-COVID-19 Syndrome: A systematic review and meta-analysis. Brain Behav Immun. 2022. https://doi.org/10.1016/j.bbi.2021.12.020
Kooij JJS, et al. Updated European Consensus Statement on diagnosis and treatment of adult ADHD. Eur Psychiatry. 2019. https://doi.org/10.1016/j.eurpsy.2018.11.001
Becker SP, et al. Report of a Work Group on Sluggish Cognitive Tempo: Key Research Directions and a Consensus Change in Terminology to Cognitive Disengagement Syndrome. J Am Acad Child Adolesc Psychiatry. 2023. https://doi.org/10.1016/j.jaac.2022.07.821
NHS Ayrshire & Arran. Signs and symptoms of a stroke. Accessed 12 November 2026. https://www.nhsaaa.net/services/services-a-z/stroke/signs-and-symptoms-of-a-stroke/
