The Top Causes of Brain Fog

You’ve probably heard people use the term “brain fog” to describe times when they felt like their brain function was slightly off. It’s often associated with symptoms like trouble concentrating, a sense of forgetfulness, issues with reaction time, fatigue, confusion, and challenges finding the right word.

So, what’s causing these problems, and what can we do about it? In this article, we’re exploring the potential drivers of brain fog and what this may mean for steps we can take to prevent and manage them.

What Causes Brain Fog? 8 Possibilities

Brain fog isn’t an official diagnosis but rather a general term for common subjective brain issues. It also isn’t one specific thing but a constellation of brain-related symptoms.

In this vein, it’s known that a host of variables can contribute to the development of brain fog. These range from infectious diseases to hormonal imbalances, vitamin deficiencies, medications, immune system alterations, and many more. We’ll focus on some of the top potential contributors to this state.

1. Mental Health Issues

Mental health issues are intrinsically linked to changes within the brain. Many criteria that are part of mental health diagnoses overlap with symptoms of brain fog (e.g., trouble concentrating in major depression and generalized anxiety disorder).

Brain fog in the context of a mental health issue could be driven in part by contributors like inflammation, metabolic dysregulation, or stress pathway dysfunction (discussed below). Seeking professional care for mental health issues should always be a top priority. Adjunct therapies that have shown promise include exercise and adopting a Mediterranean diet.

2. Long COVID

Currently, the most common driver of brain fog in the medical literature appears to be long COVID, a condition reported to affect 400 million people worldwide. Reported issues include trouble concentrating, memory issues, and confusion.

Some recent publications have described improvements in long-COVID-associated brain fog with noninvasive brain stimulation, hyperbaric oxygen therapy, and treatment with a combination of a fatty acid (palmitoylethanolamide) plus an antioxidant. It's notable that the exact mechanisms linking long COVID with foggy thinking are still under investigation, but it's likely that many cases relate to the immune activation and in particular inflammation associated with infection.

3. Endocrine (Hormonal) Imbalances

Many of the hormones that circulate through our endocrine system have direct effects on brain function. Among these, some of the most notable examples are hormones in the hypothalamic-pituitary-adrenal (HPA) axis and alterations in thyroid hormones.

As it relates to the HPA axis, the hormone cortisol is well known to influence brain state—and, when exposure is elevated and chronic, appears to contribute to impaired cognition. In the context of thyroid hormone issues, hypothyroid patients may report higher incidences of brain fog symptoms.

Along with HPA and thyroid issues, the hormonal changes and resultant issues with blood sugar seen in diabetes are known to have a strong relationship with cognitive state. In particular, having blood sugar very high, very low, or too variable may confer a higher risk for cognitive issues. Seeking qualified medical care for existing or suspected endocrine issues can help.

4. Sleep Problems

Few things can compare to sleep in terms of immediate and outsized effects on brain function. It’s no surprise, then, that poor sleep can lead to almost every symptom of brain fog. In a 2017 study, researchers found that some of these symptoms may be driven by impairments in communication between our neurons when we’re poorly rested.

Beyond simply working on better sleep, those with ongoing daytime drowsiness, consistently poor sleep quality, or other significant sleep issues should strongly consider evaluation with a sleep study to test for conditions like sleep apnea.

5. Autoimmunity, Allergy, and Infection

The immune system plays a major role in brain function. As previously described, this helps explain the rise of brain fog in the context of long COVID. However, it also allows us to appreciate the overlap between brain fog and autoimmune conditions like multiple sclerosis and lupus, allergies, and infections.

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Key to the link here is understanding that a revved-up immune system requires high energy demands and that various immune pathways can create molecules that alter brain function. For those with significant concerns for immune issues, seeking medical care is always advisable. For lower-level allergic conditions, beneficial techniques may range from allergen avoidance to over-the-counter medication.

6. Chronic Fatigue Syndrome (CFS)

CFS, also known as myalgic encephalomyelitis (ME) is defined by physical and cognitive fatigue that lasts at least six months. These symptoms are often characterized as “brain fog” by people with the condition.

Some of the potential drivers include alterations in blood flow to the brain, decreased brain activation, chronic immune activation, and poor sleep. Those concerned about significant CFS/ME should consider seeking medical care, as some cases can be improved with pharmaceutical therapies.

7. Medications

Many prescriptions and over-the-counter (OTC) medications have brain-specific effects that can mirror symptoms of brain fog. Some of the worst offenders include OTC sleep aids (especially those that contain diphenhydramine) as well as prescription sleep medications. Pain medications, especially more potent prescription drugs are known to create symptoms of brain fog.

Key considerations here are to be cautious around OTC medications and to work with your healthcare practitioner to ensure they are aware of your symptoms and to minimize excess prescription use.

8. Nutrient Issues

It’s well-known that certain nutrients are key to healthy brain function. Yet even in the 21st century, many people are at risk for developing deficiencies of these nutrients. This can lead to cognitive impairment and other symptoms of brain fog.

Some of the most important nutrients for the maintenance of brain function include B vitamins, with some research supporting a key role for vitamin D and minerals like magnesium as well. Those at higher risk for deficiencies tend to be people consuming a more limited diet, people with a history of GI disease or surgery, and high users of alcohol. Consuming a balanced diet rich in a diversity of minimally processed foods can be helpful here, but consider seeking medical care if you’re worried about a significant nutrient deficiency.

Other Strategies

In addition to the techniques described above, research supports the role of additional interventions. For example, cognitive behavioral therapy administered by a psychotherapist may help decrease symptoms of brain fog, while certain prescription drugs that act on neurotransmitter pathways may also be of benefit.

On the side of lifestyle interventions, exercise is widely touted as a brain-boosting tool that may help combat aspects of brain fog. Because of the diverse potential drivers of brain fog, working with a skilled healthcare practitioner can be an incredible asset in both determining the cause and developing a treatment plan.