The effects of brain fog can be devastating, and its causes are many and difficult to identify. It can be subtle at first, creeping into your awareness over time.
"The fog arrived slowly," says Emily, a former software analyst who asked to be identified by her first name only. She always had a good memory, never needed to be reminded of tasks, she tells LIVESTRONG.com.
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But then she noticed it was if her mind would just stop working. "Some of the very first signs were word-finding issues," she says. "I couldn't think of words like 'can opener,' 'receipt' or 'hair tie'." She would tune out and lose time.
For many experiencing symptoms similar to Emily's, brain fog is highly disruptive. But it's often equally as complicated to treat. Here, a look at what we understand so far about brain fog and what to do if you notice its effects.
What Is Brain Fog?
Brain fog isn't a disease or formal diagnosis. In fact, it's a charged issue in the medical community that's not well-defined in scientific literature.
When used colloquially, it's generally thought to mean cognitive dysfunction involving memory problems and inability to focus. That means brain fog can make people feel disoriented and mentally fatigued.
To unpack what a person means by brain fog, doctors ask about their symptoms. Unlike with better-understood health concerns, there is no test for brain fog. Doctors will likely run imaging and lab work to see if there are any underlying causes of the fog, but the cognitive changes people describe as brain fog can't be identified in an EEG or blood sample.
"While each patient may have varying clusters of symptoms — for instance intact memory in some or no difficulties falling asleep in others — the slowed thinking, disorientation and confusion and problems with focus and attention are almost always present in the vast majority of patients," says clinical neuropsychologist Michael Fearing, PhD, of Neuropsychological Evaluations of Northampton.
This makes it different from dementia, cognitive dysfunction that gets progressively more debilitating over time, as well as from chronic fatigue, which is defined as unrelenting exhaustion that isn't relieved by rest, according to the Mayo Clinic. (Fatigue also affects energy, too, not only mental sharpness.)
Possible Brain Fog Causes
Most of us have experienced the occasional bout of fuzzy thinking after a sleepless night or while battling a wicked cold. People use the term brain fog to describe the same constellation of symptoms — but it can last for years instead of hours.
Part of the difficulty of defining brain fog stems from the fact that mental confusion and ongoing cognitive issues can result from any number of common events or diagnoses, including (just to name a few):
- A traumatic brain injury, according to the Centers for Disease Control and Prevention
- General anesthesia, says Barry L. Friedberg, MD, board-certified anesthesiologist, and president and founder of Goldilocks Anesthesia Foundation
- Exposure to a food allergen, according to a May 2019 Behavioural Brain Research study
- Viral infection such as Lyme disease, according to Johns Hopkins Medicine
This means virtually everyone is at risk at some point in their lives of temporary or permanent changes in their ability to think, remember and pay attention.
And during the COVID-19 pandemic, the threat has only risen. People who had been infected with SARS-CoV-2 experienced greater cognitive decline than people without the virus over a period of three years in a March 2022 Nature study.
Then there are sequences of events that lead to brain fog that can be overlapping and multifactorial. For instance, stress can lead to a lack of sleep, which can in turn affect cognition, per Oregon Health & Science University. People commonly experience multiple conditions that can lead to problems with thinking, paying attention and remembering, Dr. Friedberg says.
Some experts theorize that many of these causes trigger cognitive symptoms in a similar way: They increase inflammation, which damages tissue, including parts of the central nervous system involved in functions like focus and memory.
How Long Does Brain Fog Last?
Regardless of their origin, brain fog symptoms can vary in severity and duration. The changes can even be permanent. “Fortunately, most postoperative brain fog resolves spontaneously in hours, days, weeks or even months,” Dr. Friedberg says.
Brain fog that occurs after a traumatic brain injury can occur immediately or weeks or months after the event, Fearing says. "In some patients, it can also demonstrate a waxing and waning pattern, when it will clear up for a period of time, but then reemerge days, weeks or months later."
How COVID-19 Is Advancing Brain Fog Research
With over 101 million cases of COVID-19 so far in the U.S. at the time of publishing, according to the World Health Organization, the long-term effects will continue to demand attention from researchers.
In preliminary November 2022 animal research in The New England Journal of Medicine, researchers found cognitive impairment in mice exposed to mild COVID similar to the type of brain effects seen after chemotherapy.
The authors suggest further research into drugs that have helped alleviate those symptoms in certain people with cancer as potential treatments for COVID-related brain fog.
They also propose investigating specific chemicals in the brain that may prove to be valuable predictors of who develops brain fog after a COVID diagnosis.
These lines of study will be important, considering if even a small percentage of COVID patients suffer significant cognitive injury, millions of Americans may be unable to work or live independently.
What to Do if You Think You Have Brain Fog
Many online resources recommend talking to your doctor if your symptoms last for several weeks and/or interfere with your daily activities. But Fearing says not to wait.
"Patients should seek medical attention immediately in order to assess the cognitive domains that are affected, as well as the severity of the cognitive impairments," he says. "It is always good practice to see your doctor and get a neuropsychological assessment" once you start noticing something seems off.
Your primary care doctor can rule out or treat possible causes of cognitive changes like vitamin deficiencies or hormonal irregularities. Because there are so many different underlying conditions that can contribute to feelings of brain fog, it's important to let your doctor know about any other symptoms you're experiencing, however unrelated they may seem.
If your doctor can't determine a direct cause of your issues, they might recommend an evaluation with a neuropsychologist.
In his practice, Fearing utilizes a number of assessments measuring memory, processing speed and the ability to pay attention and concentrate, as well as executive functions like self-restraint, planning, organization and self-motivation. The screening process can take from 3 to 5 hours, he says.
He recommends essential healthy lifestyle habits as ways to help manage symptoms, including:
"Overall there is no one magic treatment or medication, and the treatment protocol and what can be most effective varies from patient to patient," Fearing says.
If brain fog stems from long COVID, occupational and other therapists can may be able to offer some cognitive rehab, according to the Mayo Clinic.
Symptom management is part of this approach, and might include the following:
- Using sticky notes to remind you to complete regular tasks
- Keeping food journals to identify potential triggers
- Taking frequent breaks from screens
"Treatments for brain fog are really dependent on the patient, the symptoms they demonstrate and the severity of those symptoms," Fearing says. "When thinking about treatments for brain fog, it is important to assess which symptoms most interfere with the patient's social, occupational and personal functioning."
Still, practical therapy and advice has helped some patients live better with brain fog. And despite lingering uncertainty as to brain fog's causes and treatments, Fearing believes there's reason to be optimistic.
Even people with severe brain fog symptoms that last for a long time can see improvement with various lifestyle changes and other therapeutic techniques, he says.
"I have certainly witnessed this in my practice in patients who refused to give up. Yes, the longer a cognitive impairment persists, the more difficult it is to overcome. But it is certainly not impossible."
- The New England Journal of Medicine: "Cognitive deficits in long Covid-19"
- CDC: "Facts About Concussion and Brain Injury"
- Behavioural Brain Research: "Food allergy induces alteration in brain inflammatory status and cognitive impairments"
- Brain Injury Association of America: "COVID-19 resources for people with brain injuries"
- Mayo Clinic: "Mayo Clinic Q&A podcast: 'Brain fog' is a lingering condition for many COVID-19 long-haulers"
- Johns Hopkins Medicine: "Visualizing ‘Brain Fog’ in Post-Treatment Lyme Disease"
- Nature: "SARS-CoV-2 is associated with changes in brain structure in UK Biobank"
- OHSU: "Brain Fog vs. Dementia"
- Cell Stem Cell: "Human Hippocampal Neurogenesis Persists throughout Aging"
- World Health Organization: "Coronavirus (COVID-19) Dashboard"
Is this an emergency? If you are experiencing serious medical symptoms, please see the National Library of Medicine’s list of signs you need emergency medical attention or call 911.