15 Hidden Causes of Brain Fog You Must Know About (Science-Backed)

brain fog

15 Hidden Causes of Brain Fog You Must Know About (Science-Backed)

You’ve most likely had a minor episode of brain fog at one point or another in your life. Have you walked into a room and forgot why you went there? Perhaps you’ve scoured around your home for your keys only to find them in your pocket, or a neighbour’s name slipped your mind, but it’s on the tip of your tongue. If so, you’re not alone, and there is a name for this condition.


What is Brain Fog
What Causes Brain Fog

  1. Leaky Gut Syndrome
  2. SIBO
  3. Candida Overgrowth
  4. Poor Thyroid Function
  5. Fluctuating Blood Sugar Levels
  6. Vitamin B12 Deficiency
  7. Inflammation of the Brain
  8. Hormonal Changes
  9. Stress
  10. Sleep Deprivation
  11. Medication
  12. Limbic System Imbalance
  13. Circadian Rhythm Disruptions
  14. Obesity
  15. Infections

Bottom Line

What Is Brain Fog?

These mild periods of forgetfulness or confusion are generally just mild annoyances you can live with, and they don’t usually mean anything huge. However, they can start to get more debilitating, and this is a condition called brain fog, cognitive dysfunction or clouding of consciousness.

It’s not a medical term but rather a generalised term for problems of focus, memory and learning that can easily create brief episodes of disorientation, frustration and confusion. You might find yourself struggling to get the words out to describe something or feel disorganised. Other common symptoms of brain fog include:

  • Low motivation levels
  • Poor working memory
  • Difficulty making decisions
  • Wandering thoughts
  • Inability to focus on a single train of thought
  • Disorientation
  • Poor recalling and memorisation abilities
  • Frustration
  • Irritability
  • Chronic fatigue
  • Body aches
  • Feeling overwhelmed

In other words, you feel “foggy.” There are no concrete tests to or exact medical diagnosis for brain fog because the severity and frequency varies wildly from person to person. This makes it very frustrating for people who are experiencing these symptoms, especially if they’re getting more frequent and interfering with everyday life.

However, there are several science-backed causes of brain fog, and it’s a good idea that you understand them, so you know which direction to point your doctor in in the event that you find yourself with a more severe case of brain fog. This will help you get ahead of your symptoms and start working on a cure for whatever is causing your specific case of brain fog.

What Causes Brain Fog?

It’s true that brain fog can be a symptom of a larger ongoing issue, and depending on what this issue is, there are steps that you can take to reduce the severity of your brain fog. It’s usually not just one issue that causes brain fog, and this adds to the complexity of this issue. It’s also why it may take a while to get a proper diagnosis because you have to find and treat the underlying cause to treat your brain fog.

1. Leaky Gut Syndrome

Leaky Gut Syndrome is a is another blanket term used to describe a variety of gastrointestinal issues. This syndrome is characterised by cracks or fissures in the lining of the intestines that cause system-wide inflammation. This is why you may hear leaky gut syndrome called intestinal permeability as well. Complications from this syndrome include things like inflammation, pain, food sensitivity, IBS, autoimmune disease, skin problems, depression, hypothyroidism and even brain fog or an altered mental status.

Since one of the major indicators that you have leaky gut syndrome is having chronic, system-wide inflammation, it makes sense that it has strong links to brain fog. This is because inflammation and infection typically go hand-in-hand, and inflammation is your body’s way of fighting off what it identifies as a threat.

Inflammation from leaky gut can disrupt the normal neurotransmitters that communicate between your nerve cells. In turn, this disruption can cause forgetfulness, confusion and frustration as you realise that you’re forgetting things. Infections are also common with leaky gut because of the intestinal permeability that comes with this syndrome, and it can cause sudden brain fog as well.


SIBO, or Small Intestinal Bacterial Overgrowth, is a condition where masses of colonic-type bacteria (or bacteria found in your colon) end up in your small intestine. There are several causes of this condition including a dysfunction of your intestinal muscles or nerves, a bypassed small intestine, or an obstruction. While there are always healthy amounts of bacteria throughout your entire digestive tract, SIBO can double or even triple the normal amount. Complications from SIBO include things like food allergies from immune system reactions, bloating, gas, food sensitivity, autoimmune diseases and inflammation.

few studies examined the links between people with gas, bloating or conditions like SIBO and brain fog. In the study, participants with the above symptoms or conditions were monitored and recorded for episodes of brain fog. The researchers found that people with these health issues displayed more brain fog episodes than healthy people.

They found that when the SIBO bacteria count was at its highest, the bacteria released histamine. Histamine can cause feelings of brain fog. Knowing this, it makes sense that once the people started treating their SIBO, the episodes of brain fog dropped as the level of histamines in their body dropped.

3. Candida Overgrowth

Candida Overgrowth is often referred to as Candidiasis. This is a fungal infection, and there are currently over 20 different species of Candida fungus that are able to cause infections in humans. You can normally find Candida yeast in your GI tract and in your skin in the mucous membranes. When they overpopulate, you get a yeast infection or Candida overgrowth. Symptoms vary from person to person and in severity, but common symptoms include fatigue, urinary tract infections, digestive system issues like constipation, gas and bloating, and skin or nail fungal infections.

Johns Hopkins Medicines published a study that showed common symptoms of Candida overgrowth could cause brain fog in varying degrees. They did note that brain fog was more common in the male patients with diagnosed mental illnesses, but it did occur in participants that didn’t have a mental illness as well.

They also found that the inflammation caused by Candida overgrowth can cause a significant disruption in the nervous system, particularly with the neurotransmitters. When this disruption happens, you get short periods of brain fog. If your inflammation gets worse, your brain fog can worse.

4. Poor Thyroid Function

Everyone has a thyroid. This glad is located at the lower front of the next. It’s butterfly-shaped, and this endocrine gland makes hormones. These hormones get into your bloodstream and go to every tissue in your body. Thyroid hormones help your body in several ways including helping your body use energy and keep your organs like your heart, brain and muscles working in top condition. Unfortunately, thousands of people around the world have poor thyroid function, and this can lead to a variety of problems.

For people with poor thyroid function or Hypothyroidism, the chances of suffering from periods of brain fog are extremely high. Brain fog is actually one of the first and biggest clues that your thyroid gland isn’t functioning correctly.

This is because your thyroid gland has strong ties to your metabolism. Once your metabolism starts to fluctuate because of thyroid problems, your energy levels drop. When your energy levels hit a certain low, your brain is one of the first organs to feel the impact. This can result in brain fog episodes including confusion, mood swings and general forgetfulness.

5. Fluctuating Blood Sugar Levels

Blood sugar is also called glucose, and it’s the main sugar that is found in your blood. This sugar is where your body gets most of its energy, and you get it from the food you eat. Once your body breaks down this sugar in your blood, it travels throughout your body to all of the cells to give them energy so they can perform their required processes. For people with Hypoglycemia or Diabetes, they can experience wild fluctuations in their energy levels, and this can lead to lack of energy, anxiety, memory problems and coordination problems.

Unfortunately, brain fog has direct ties to your blood sugar levels, and it can get worse or better as your blood sugar levels fluctuate from one extreme to the next. As your blood sugar fluctuates, your cells and neurotransmitters will either overload from too much sugar or not have enough energy to perform their tasks.

One study showed that people with chronic blood sugar control issues and wild fluctuations are more likely to experience prolonged periods of confusion, forgetfulness or mood swings. They did note that as the participants learned to control their blood sugar levels, their periods of brain fog went down.

6. Vitamin B12 Deficiency

The nutrient that helps to keep your body’s cells and nerves healthy is Vitamin B12. It also plays a significant role in helping the body make DNA. This nutrient comes from proteins that you eat, and your stomach acid will break it down so your body can absorb it. Unfortunately for a lot of people, not having enough of this nutrient can wreak havoc in your entire system.

Roughly 1 in every 10 people have a Vitamin B12 deficiency in some form or another, and the consequences can be severe. Vitamin B12 helps to keep your nerves and your neurotransmitters working as they should. When there isn’t enough of this nutrient to go around, your nervous system is one of the first things that gets impacted.

The New England Journal of Medicine reported a case of a man who was deficient in this nutrient. He started experiencing tingling in his extremities, irritability and it slowly progressed to brain fog. If you don’t get treatment for this deficiency, you can experience severe memory loss, paranoia, delusions, loss of taste and more.

7. Inflammation of the Brain

If you experience period or chronic brain inflammation, you’ll have periods where parts of your spinal cord and your brain trigger and become inflamed. Sometimes, you’ll have a specific trigger that sets off the inflammation like an infection or injury, and other times your brain will get inflamed in response to something happening somewhere else in your body. People who have mental illnesses are closely linked to brain inflammation, and this inflammation can cause a variety of symptoms including whole body fatigue, unspecified pain, disorientation, confusion, nausea, hallucinations and more.

Brain inflammation is also called Encephalitis, and it’s usually a response to a person’s immune system overreacting or an infection. When this happens, the inflammation can disrupt the brain’s normal processes, and this can cause the common symptoms that are typical of brain fog including trouble concentrating or remembering things and general confusion.

One study showcased the role of brain inflammation and memory in rats. During the study, scientists found that the inflammation disrupted the normal neurological processes of the rats. This disruption caused the rats to act confused and disoriented. As the inflammation went down, the brain fog symptoms decreased as well. This demonstrated the positive links between brain fog and brain inflammation.

8. Hormonal Changes

You can go through a variety of hormonal changes throughout your life. Two big reasons why you would experience these hormonal changes are puberty and menopause. Thyroid issues can also cause hormonal imbalances. Puberty and menopause affect both men and women, and the fluctuating estrogen and testosterone can wreak havoc on your entire system from your central nervous system to your lymphatic system. This can result in the common symptoms that can last for years.  

One study showed that women who were going through the beginning stages of menopause experienced several cognitive changes. This study showed that women have problems with working memory tasks, motor function, attention and verbal learning. These problems can get worse as puberty or menopause progresses, and then they get better as you go through menopause and complete it. 

Another study revealed that hormone changes can negatively impact various systems throughout your body, and this can lead to mood disorders, depression, fatigue, anxiety, inflammation, abdominal pain, gas, bloating and diarrhoea.

9. Stress

When you have a lot of demands and you feel overwhelmed, you’re stressed. Stress can come from both good and bad experiences, and when you react to stress, your body releases a flood of chemicals. Stress is a bad thing if it’s a response to something harmless and not actual danger, and stress can cause several physical and mental problems. This is especially true if you have chronic stress. Physical and mental stress symptoms include fatigue, being emotional, body aches, hair loss, a weakened immune system and high blood pressure.

People with chronic fatigue syndrome and high levels of stress have a higher chance of developing more severe periods of brain fog. This is because when your brain has lower energy levels or when it’s exhausted, it gets harder for you to think, focus or reason. This leads to brain fog, and it can get worse as your stress levels get worse.

A study showed that constant exposure to stress can wear away at your energy reserves and it can also make you more immune to infections. When your immune system is weak, you can experience inflammation that can spread throughout your body from infections. This can take your slight brain fog and make it much worse until you start to manage your stress levels.

10. Sleep Deprivation

If you’re sleep deprived, you’re simply not getting enough sleep each night. The longer you go without getting adequate amounts of sleep, the harder it’ll be for you to focus, concentrate and remember things. You’re not alone if this applies to you, roughly 1 in 3 Americans suffer from chronic sleep deprivation. If this goes on for a long time, you’ll start to experience several symptoms like irritability, fatigue, paranoia, depression, anxiety, overeating, increased risk of diabetes, increased risk of cardiovascular problems and brain fog.

For people who have sleep deprivation due to stress, their job or their lives, the chances of developing brain fog and complications are increased. Trouble with your memory and decreased cognitive function are two big indications that you’re sleep deprived, and they can cause a lot of frustration.

One study showed that sleep deprivation can decrease your cognitive function by reducing your energy levels and making it difficult for your neurotransmitters to function at their optimal levels. It can also make you forget things because sleep is essential to memory storage and function, and if it doesn’t have time to process your memories and store them each night, you run a high risk of forgetting them. It’s also more difficult to learn because your attention span drops, and your short term memory capacity reduces.

11. Medication

Depending on your condition, certain medications can cause brain fog. It’s usually one of the less harmful side effects of your medications, and it can take a while to come on. Common medications that can cause brain fog are opioid pain medications like oxycodone or morphine,  benzodiazepines like lorazepam and xanax, prescription sedatives like Lunesta and Ambien, over-the-counter sleeping aids, and antipsychotics like Abilify or Seroquel. There are alternatives that you can take to help manage your condition without getting the brain fog side effect.

Several of these medications can interfere with the neurotransmitter acetylcholine in your brain. This neurotransmitter is a chemical messenger that has several important functions throughout your body, and these include cognitive function and your memory. When this neurotransmitter gets interrupted, you experience various symptoms of brain fog.

study showed that elderly people are more likely to have medication-induced brain fog, but this is because they’re usually on more medications than the younger population. The brain fog ranged from acute to chronic confusion, and they observed that the symptoms fluctuated as the medications changed.

12. Limbic System Imbalance

Your limbic system is an extensive network of networks and nerves in the brain. It involves several areas along the edges of your brain’s cortex, and they primarily focus on mood and instinct. This system controls emotions like anger, fear and pleasure along with common drives like dominance, sex and care for your children. Your limbic system is home to your hypothalamus, which is known as the control centre for your entire brain, and this is the area that is most affected by a limbic system imbalance.

Imbalances in the limbic system are usually due to high and chronic stress levels or a significant brain injury. If this happens, you can experience several symptoms that range from mild to severe depending on the stress or injury level. Common symptoms include depression, anxiety, fatigue, increased blood pressure, mood swings, thirst, overeating and problems with your memory and recall.

Researchers focused on the effect of an imbalanced limbic system and the severity of brain fog. They found that people who had known imbalances in their system displayed more severe brain fog symptoms. They had trouble with their recall, learning new tasks, attention spans and their memories in general. This led to frustration as the symptoms got worse.

13. Circadian Rhythm Disruptions

Your circadian rhythm refers to the internal 24-hour clock that automatically runs in the back of your brain. Have you noticed that you tend to feel drowsy or energised at certain points during the day? If so, this is your circadian rhythm. This is your sleep/wake cycle, and it’s important for your mental and physical health that it stays relatively consistent without any major interruptions. However, sleep deprivation can cause wild fluctuations and variations in this natural rhythm, and this is where you start to experience problems. 

Common disruptions to this natural rhythm include working second and third shifts, sleep deprivation, introducing artificial lighting, sleep disorders like insomnia, jet lag, pregnancy, medications, Alzheimer’s disease, Parkinson’s disease and mental health problems. The more disrupted your circadian rhythm gets, the more severe your brain fog problem can be.

recent study with animals showed that circadian rhythm disruptions can have negative impacts on your memory and learning capabilities. They found that participants experienced difficult recalling things and forming memories the longer their circadian rhythms were out of whack. When they started regulating their circadian rhythm or reset it, they experienced a decrease in their brain fog symptoms.

14. Obesity

Obesity is a condition where you have a lot of excess body fat combined with environmental and genetic factors that make it difficult to control through exercising and diet. Obesity has several ways to diagnose it, but one of the most common ways is called Body Mass Index (BMI). There are roughly 1 in 3 adults are considered obese, and this number continues to rise each year. Obesity is a problem for both children and adults all around the world.

Obesity comes with an increased risk of both mental and physical health problems. These include things like early death rates, cardiovascular issues, high blood pressure, breathing problems, sleep apnea, depression, anxiety, body pain, brain fog and more. These symptoms can get worse as you get more overweight, and it’s difficult to lose the excess weight.

Since obesity can lead to chronic inflammation, it can disrupt your brain’s neurological function. This leads to disrupted neurotransmitters and problems focusing, memorising things and recalling information. You’re most likely not getting all of the nutrients you need either, and this can cause problems with brain fog, or it can worsen your symptoms.

15. Infections

Infections can be bacterial, fungal or viral in nature, and people are starting to notice links between infections and autoimmune conditions. Infections are caused by various microorganisms like bacteria, fungal agents or viruses. They invade your body in order to multiply and make you sick. If you have a weak immune system, you’re more vulnerable to various infections because your body isn’t as adept at fighting them off. Infections can bring fatigue, brain fog, a weakened immune system, respiratory problems and joint pain.

Unfortunately, infections can also cause system-wide chronic inflammation as well as oxidative stress. Some bacterial infections can cause your body to overproduce inflammatory cytokines, and this can disrupt your normal body processes. These infections can also increase TNF and Il-6 in your system.

Studies showed that infections can cause sudden onset delirium or confusion, problems recalling things, trouble concentrating or trouble learning new things. The study showed that these symptoms can continue for as long as the infection is active, and you should start to see a decrease of your symptoms and your brain fog in general when you start to treat the underlying infection.

Bottom Line

Brain fog can be an annoyance at best and debilitating at its worst and you can experience both ends of the spectrum. It’s a good idea to talk to your doctor if you experience it, and they can help you narrow down the cause or causes so you can start treating it. It may be something as simple as stress or sleep deprivation, or it may be something more complicated like poor thyroid function or hormone changes.

No matter what it is, getting to the root cause can help to alleviate they brain fog symptoms that you experience, and this can help you live a fuller life because you won’t be excessively worrying about it. You can also try minor things on your own and see if they help. Either way, you’ll be actively working toward a healthier and happier life.

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