What Is Brain Fog in ADHD?

Some mornings I wake up and the inside of my head feels full of cotton. My sentences stay half-finished, I cannot find a word I know, even the question "what shall I have for breakfast" feels heavy.

On those days, what tires me most is not the fog itself. It is trying to get through a normal day inside the fog. Because the calendar is the same calendar, the deadline is the same deadline.

In everyday language this is called brain fog. In this article I want to separate both what it is and what it is not, because when the two get mixed up, something really treatable can be missed.

First, a note for the record

Brain fog is not a medical diagnosis. There is no such heading in diagnostic manuals, no criterion, no test.

It is a description. What it describes is real and quite concrete for the person living it, but it has no single cause. That is why the sentence "I have brain fog" is not enough as an explanation. It helps to think of it like a headache: a headache is real too, but the sentence "my head hurts" does not say why it hurts.

For a long time I took this sentence to be an explanation. "I have ADHD, days like this happen," I would say and move on. Now I ask myself: where did this fog come from today?

Why it is described so often in ADHD

Sleep. The most common cause. The review by Kooij and Bijlenga (2013) shows that a delayed sleep phase is often seen in adult ADHD. The most typical symptom of chronic sleep debt is exactly this blurriness. I dealt with the reasons for going to bed late separately in the article on why we go to bed late; it took me a long time to notice that most of my foggy days were decided the night before.

Overload. A kind of shutting down that comes after a long meeting, a crowded environment or successive interruptions. When the mind fills its capacity it switches itself off. I went into this in more detail in the article on sensory overload.

Burnout. The result of working above capacity for a long time. This fog does not last a single day; it lasts for weeks and does not pass quickly with rest. The article on burnout in ADHD is about this picture.

Emotional fatigue. The emptiness that comes after a heavy wave of emotion. The mind running empty the day after a hard conversation is very familiar to me.

The crash after hyperfocus. The blurriness that comes after sinking into a job for hours. The bill for four hours that passed without a break, without eating, without getting up usually arrives the next morning.

The medication wearing off. People who take stimulant medication can describe a temporary blurriness in the hours when the effect ends. In the glossary it is under rebound. The medication decision and the timing schedule are something to talk about with the doctor.

Brain fog is most often not a symptom but a bill. It comes as the price of something, and finding out the price of what is more useful than dealing with the fog itself.

When another cause should be looked for

This is the most important section of the article and the place I do not want skipped.

If brain fog is persistent, severe or has increased markedly recently, the following need to be investigated before attributing it to ADHD:

• Thyroid dysfunction
• Iron deficiency and B12 deficiency
• Sleep apnea (especially if there is snoring and daytime sleepiness)
• Depression
• Side effects of some medications
• Hormonal periods, which I covered separately in the article on the menstrual cycle and hormones

The systematic review by Instanes and colleagues (2018) reports an association between adult ADHD and some physical health problems. Katzman and colleagues (2017) emphasize that accompanying conditions are not the exception but the rule.

What comes out of this is this: the answer "I have ADHD, that's why I am like this" is comforting but risky. Most of the list above can be ruled out with a doctor's appointment and a few blood tests. The decision about diagnosis and treatment is the doctor's job; my job is to go with the right question.

What I do on a foggy day

I learned by trying quite a lot that forcing myself on these days does not work. Forcing only produces guilt in the evening.

I put off decisions. The decisions I make on a foggy day are not good ones. Quoting a price, answering an important message, accepting a job; I leave these for the next day.

I look at the list, not at memory. Working memory, already weak, does not suffice at all that day. Everything written down becomes more valuable that day.

I choose a single job. Instead of starting three jobs and finishing none, one small job. A small finished job feels much better than a big unfinished one.

I move the body. A short walk, going outside, drinking water, eating something. On those days the simplest interventions are the ones that work most.

I lower the expectation. This is the hardest for me. Trying to produce a normal day's work on a foggy day does not save the day; it eats the next day too.

I note the cause. What happened yesterday: did I sleep little, was it crowded, was there a hard conversation, was there a long stretch of focus?

Fog or the usual scatteredness

Telling these two apart saved me quite a lot of time.

In my usual inattention my mind works fast, it just does not stay in one place. Lots of ideas, lots of jumping, lots of leaps. On a foggy day it is the opposite: the mind slows down, ideas do not come, I have to wait to form a sentence.

The distinction works in practice. On a scattered day, simplifying the environment and multiplying external reminders helps. On a foggy day the same moves change nothing; there the real matter is rest and finding the cause. If you apply the same prescription to two different situations you fail in both and you write it down against yourself.

Finding the pattern

Keeping a simple record for a month was the thing that helped me most on this subject:

• Was today foggy (yes/no)
• How many hours I slept
• What happened yesterday

Three columns are enough. If I try to build a more detailed table I quit in two days, so I keep it small. After a few weeks the pattern becomes visible, and once the pattern is visible you can take precautions: instead of waiting for the fog to come and being surprised, leaving the day after whatever triggers a foggy day empty, for example.

The clearest thing that came out of my own record was this: the cause of the fog is often not that day but the two days before. I covered the general picture of the question of tiredness in a separate article.

What I keep in mind

Brain fog is not a diagnosis, it is a description. It is common in ADHD but most of the time it does not come from ADHD itself; it comes from lack of sleep, overload and burnout.

If it is persistent and severe, there are other causes that are easy to rule out and possible to treat. They should not be passed over without looking. Some of the things I explained for years with "that's how I am" turn out to have another explanation; after learning this I began to look at myself with a little more curiosity.