Secondary contributors to Brain Fog

Mental Fatigue (associated with Post-Viral Fatigue / or Post-Covid Fatigue)

When experiencing post-viral fatigue, it is difficult to think, concentrate or take in new information. Basic word finding and thinking can be difficult. Energy is required for mental and cognitive activity, similar to running out of energy when doing a physical task people cannot cope with longer periods of mental/cognitive activity and start to lose concentration and ability to process and retrieve information.

A useful analogy to explain fatigue as the cause of brain fog is that of the filing clerk/filing cabinet. It can be helpful to think of your brain as a filing cabinet and your mental processes as the filing clerk. With fatigue, the filing cabinet (the brain) is not necessarily damaged; it’s just that the filing clerk has been slowed down (meaning your brain structure is fine, however your mental processes are not working as effectively because they are tired).  


Scientific evidence supports the notion that pain negatively affects cognitive ability. While temporary pain doesn’t impact cognition much, persistent pain can cause changes in the brain systems that control cognitive function. Studies have shown that pain can disrupt several cognitive processes, leading to problems in attention, spatial memory, recognition memory and decision making. Pain can be consuming and distracting and can make it more difficult for people to perform cognitive and memory tasks. Pain can also increase levels of stress hormones like cortisol, which has been shown to affect brain cell structure.  

Side Effects of Medications

Some medications can cause tiredness and cognitive difficulties. Typical culprits include opioids, antihistamines, tricyclics, benzodiazepines, Z drugs, sedative anti-depressants and anti-psychotics.

  • Benzodiazepines (prescribed for anxiety) act directly on the parts of the brain that convert short term memories into long term memories.
  • Statin drugs lower cholesterol everywhere in the body, including in the brain, where cholesterol is needed for connections between nerve cells.
  • Narcotics – Narcotic painkillers change chemical signals associated with cognition.
  • Beta Blockers to treat hypertension also block chemical messages in the brain, such as neurotransmitters.
  • Non-Benzodiazepine Sedative-Hypnotics prescribed for sleep can act on many of the same brain pathways and chemical messengers as benzodiazepines. Sleep aids can also cause amnesia and sometimes trigger strange behaviours, such as cooking a meal or driving a car with no recollection of doing so.


A medication review and detailed drug history by GP is advised.

Poor Sleep or Sleep Deprivation

Impaired sleep is common in those who have been medically unwell or those who have been through stressful circumstances. Poor sleep, leading to tiredness and fatigue, can adversely affect thinking ability. Poor sleep habits and sleep deprivation can contribute in several ways to brain fog and cognitive dysfunction. The process of sleeping is required to clear toxins from the brain; to build new neural connections; and to process and consolidate new learning and memories. Sleep deprivation has been shown to cause significant drops in memory and reduced hippocampus volume (the area of the brain responsible for consolidation of short-term memories and formation of long term memories). Managing your sleep is important in maintaining optimal cognitive function.

Dietary Issues or Nutritional Deficits

Brain fog can occur as a result of nutritional deficiencies and a lack of the vitamins required for healthy brain function. Eating patterns that involve skipping meals may contribute to mood swings by causing fluctuations in blood sugar levels and low glucose in the brain can also lead to brain fog. Food restriction can lead to binge eating, bigger emotional responses, poor concentration, increased stress, and an overall lower sense of well-being. Inflammatory foods can also increase the proinflammatory cytokines in the blood and brain leaving you with low-grade inflammation that can manifest as a foggy brain. Being overweight can also contribute to inflammation. Inflammation stresses your body and rapidly uses up nutrients, specifically the B vitamins, magnesium, and vitamins C and E.

Stress and Anxiety

Anxiety and stress can have a considerable impact on cognitive functioning, memory and concentration. Atrophy of brain regions, resulting from repeated exposure to stressful conditions, has a cognitive cost. Working memory, attention, response inhibition and cognitive flexibility have all been found to be impaired by stress.  

Low Mood

Depression can have an impact on cognitive functioning and can affect a person’s capacity to concentrate and focus, as well as remember key information. Studies have shown that many patients with depression report significant cognitive deficits, including deficits in executive function (problem solving, decision making, and judgment), memory, and attention to daily activities.

Social Isolation

People who feel lonely or disconnected from others have been shown to have faster rates of cognitive decline than people who don’t feel lonely. The mechanisms that link social isolation with poor cognition may include the detrimental effect of a lack of social stimulation on the brain (reduced verbal fluency, memory and recall) which may result in lower cognitive reserve, poorer resilience of the brain, and cognitive decline.

Alcohol, Nicotine or Illicit Substance Use

Excessive alcohol use (binge drinking and/ or consuming more than 14 units a week) and use of illicit substances can contribute to cognitive difficulties. Stimulant drugs, like nicotine and amphetamine, improve cognitive function at lower doses but impair memory performance at higher doses. Depressant drugs, like alcohol, can cause long-term effects on prefrontal cortex function, disrupting cognitive abilities.

Mental Over-Exertion

Mental over-exertion leading to mental fatigue has been shown to increase feelings of tiredness, lack of energy, decreased motivation, and alertness which can negatively influence performance and cognitive functioning. These can include problems with memory, attention, processing speed, language comprehension and word-finding abilities, among others.

Physical Inactivity or Under-Exertion

One of the cognitive benefits of exercise is that it enables you to cope with life’s challenges. Exercise can help boost thinking and memory indirectly by improving one’s mood and reducing stress, depression, and anxiety. Aerobic exercise has been shown to decrease feelings of depression, anxiety, and stress. Exercise also oxygenates and clears toxins within the body.