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7 Ways Toxic Mold Affects Your Brain


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Diet, sleep, physical activity, stress management—as advocates of an ancestral diet and lifestyle, we know well that these factors have a significant impact on our cognitive function. However, have you ever stopped to think about how your indoor environment might be impacting your brain?

mold effects brain
Mold exposure can cause a number of effects in the brain, including fatigue and depression. iStock/Cecilie_Arcurs

This article originally appeared in Paleo Magazine

The average person living in the modern, Westernized world spends a whopping 80 to 90 percent of his or her time indoors. (1) Given the amount of time we spend inside, we must ensure the safety and cleanliness of our indoor environments. Unfortunately, a shocking number of residential buildings, schools, and workplaces today harbor an environmental contaminant that poses a severe threat to our cognitive health—mold. Read on to learn why the sharp smell of mold and unpleasant musty odors indoors should not be ignored if you care about your long-term cognitive health.

Exposure to toxic mold can cause a number of worrying cognitive symptoms. Check out this article to find out more and to learn how to seek treatment. #functionalmedicine #chriskresser

Indoor Mold: A Threat to Our Health

According to the World Health Organization, up to half of the buildings in North America are water damaged and, thus, prime “real estate” for indoor molds. (2) Molds such as Stachybotrys chartarum and Aspergillus thrive in damp environments rich in porous materials, such as particleboard, wood, and drywall. In the presence of these materials, a small water leak from a poorly sealed window or a hole in a basement foundation is all it takes to trigger a bloom of mold growth, with potentially drastic repercussions for residents’ health. (3)

Once mold has established itself in a water-damaged indoor environment, it begins to release secondary metabolites called mycotoxins. Examples of mycotoxins include trichothecenes, produced by the Fusarium fungus, and gliotoxin and ochratoxin A, produced by Aspergillus fungi.

Mycotoxins pose a serious threat to human health, particularly when they are inhaled, swallowed, or absorbed via dermal contact in moldy buildings. The adverse health effects of mycotoxins are compounded by the presence of other biotoxins in damp buildings, including bacterial endotoxin, fungal and bacterial cell wall fragments, and microbial volatile organic compounds (VOCs). (4)

The constellation of symptoms caused by mold and biotoxin exposure is referred to as “mold illness,” “biotoxin illness,” or chronic inflammatory response syndrome (CIRS). While mold and mycotoxins impact diverse body systems, the cognitive effects are among the most disconcerting.

An Evolutionary Perspective on Mold Illness

Humans have interacted with environmental molds throughout our evolutionary history. As a result, our bodies have developed natural defense systems for addressing these toxins, including the mucociliary clearance mechanism in the lungs and the innate and adaptive branches of the immune system. However, in an unwitting example of evolutionary mismatch, our natural defense systems are no match for the potent mold strains found in the modern buildings in which we work and live. These buildings are designed in ways that promote mold growth, with poor airflow and myriad opportunities for water leakage. Most peoples’ defense systems cannot keep up with chronic mold and mycotoxin exposure, causing them to succumb to illness.

The cognitive symptoms of mold exposure also have an evolutionary component. Mold illness triggers an evolutionarily conserved phenomenon called “sickness behavior,” which includes sleepiness, depression, apathy, and social withdrawal.

Mold-induced sickness behavior is the result of an immune response that is intended to help you survive the current mold exposure and avoid future exposures. (5) However, many people do not make the connection between their symptoms and their environment, instead living in a vicious cycle of constant mold exposure and illness.

Your Brain on Toxic Mold: Seven Effects of Mold Illness

A brain exposed to toxic indoor mold and mycotoxins is typically not a very happy brain. Research indicates that the spectrum of cognitive impairments caused by mold and mycotoxin exposure are extensive. Many of these mental health conditions are quite prevalent in our society. This should make us wonder how many of these cases might be due to toxic environmental exposures, such as mold.

1. Cognitive Impairment

Mold and mycotoxin exposure have been found to reduce memory capacity, attention, and intellectual capacity, as assessed by IQ tests. (6)

2. Chronic Fatigue

Patients with chronic fatigue syndrome have high urinary mycotoxin levels, suggesting that mycotoxins may play a role in the disease process. (7)

3. Neurodegenerative Diseases

The groundbreaking work of Dr. Dale Bredesen has revealed that mycotoxins participate in the pathogenesis of a subtype of Alzheimer’s disease, referred to as “inhalational Alzheimer’s disease.” (8) Fungi may also play a role in the development of amyotrophic lateral sclerosis and Parkinson’s disease. (9, 10)

4. Depression and Anxiety

A study of over 5,000 adults published in the American Journal of Public Health found that those living in moldy environments had significantly higher rates of depression compared to controls living in mold-free environments. (11) Many of the mold-exposed people with depression also suffered from anxiety.

5. Autism

Emerging research indicates that children with autism have higher urinary levels of mycotoxins compared to their peers without autism, suggesting a relationship between mold exposure and autism. (12)

6. Psychosis

The relationship between mycotoxins and psychosis has been documented throughout human history. In the Middle Ages, exposure to ergot alkaloids caused a hallucinatory illness called “St. Anthony’s Fire.” Early North American settlers who ate mold-contaminated grain were also known to suffer psychotic episodes. (13)

7. Traumatic Brain Injury

Several of the neurological impairments that occur in mold illness resemble impairments observed in traumatic brain injury, including impaired learning and reduced psychomotor speed. (14)

Mycotoxins and the Brain: Mechanisms of Action

There are several mechanisms by which mold and mycotoxins harm the brain and induce cognitive dysfunction.

  • Mycotoxins induce oxidative stress, instigating the release of reactive oxygen species from cells that cause damage to nervous system tissue. (15)
  • Trichothecenes induce mitochondrial dysfunction, a phenomenon that has been found to underlie cognitive impairment. (16, 17)
  • Mycotoxins interact with the neuroimmune axis, a network of cells and signaling molecules that links the immune system with the central nervous system. Mycotoxins activate mast cells along this axis, triggering the release of inflammatory cytokines that cause neuroinflammation and cognitive dysfunction. (18)
  • Mycotoxins impair neuronal plasticity by binding to proteins involved in synapse activity. Reduced neuronal plasticity is a contributing factor in cognitive dysfunction, depression, and anxiety, among other mental health issues. (19)
  • Mycotoxins compromise the integrity of the blood–brain barrier, crossing into the brain and exerting neurotoxic effects on neurons. (20, 21)

Is Mold Harming Your Brain? What to Do Next

Do you suffer from unexplained cognitive symptoms and suspect that mold might be a cause? To prevent overwhelm and quickly devise a course of action, follow these steps.

1. Create a Timeline

Create a timeline that includes all the buildings you’ve worked and lived in, charted together with the appearance of your cognitive symptoms. Did any of the buildings harbor visible mold, sustain water damage, or smell musty or moldy to you? Do your symptoms line up with the time you spent in these buildings? If yes, then mold exposure may indeed be contributing to your cognitive or mental health difficulties.

2. Find a Clinician Who Is Familiar with Mold Illness

Many physicians (even Functional Medicine practitioners) are still unaware of mold illness, so you’ll need to find a practitioner who is “mold-literate” and can assess you for mold and mycotoxin exposure. I recommend checking out the International Society for Environmentally Acquired Illness website to find a qualified practitioner.

3. Test Your Current Environment for Mold and Mycotoxins

This step can get pretty confusing, as there are many types of mold and mycotoxin tests out there, and many different companies offering environmental assessments of varying qualities. While the Environmental Relative Moldiness Index (ERMI) test has long been considered the “gold standard,” it tests only for mold, not mycotoxins. Instead, I suggest doing an Environmental Mold and Mycotoxin Assessment (EMMA). The EMMA tests for both mold and mycotoxins, and it assesses for all clinically relevant organisms using quantitative polymerase chain reaction. If you’d rather have a professional guide you through the testing process from the get-go, I recommend getting in touch with indoor environmental professional Michael Schrantz of Environmental Analytics.

4. Remove Yourself from the Contaminated Environment and Begin Treatment

Removing yourself from the mold- and mycotoxin-contaminated environment is the first step toward healing. Next steps, guided by a mold-literate practitioner, may include taking binding agents to “mop up” circulating mycotoxins, treating fungal infections, and using Functional Medicine to address the downstream effects of mold/mycotoxin exposure.

Mold illness is scary, especially when it starts to impact your most precious organ, your brain. However, there is no need to panic. By following the actionable steps outlined here, you can take charge of your well-being, address toxic mold exposures, and restore your cognitive health.

More about Mold Illness and Its Effects on the Brain

  1. Ergotism, a poisoning caused by eating foods contaminated with a group of mycotoxins called ergot alkaloids, may have triggered the bizarre hallucinations of early North American settlers that led to claims of “witchcraft” and the infamous Salem witch trials. While the fungus responsible for ergotism, ergot, grows primarily on grains, mycotoxins from indoor molds may also cause psychosis. (22)
  2. The ghost sightings and other paranormal experiences of people who have lived in “haunted” houses may, in fact, be due to neuropsychiatric dysfunction induced by neurotoxic mycotoxins and molds growing in these homes, which are often quite old, dark, and damp. (23)
  3. Climate change is creating more damp indoor environments, due to phenomena such as floods, as well as triggering the evolution of more virulent indoor molds. Scientists suspect that the incidence of “mold hypersensitivity syndrome” will rise as our planet’s climate continues to warm up. (24)
  4. Finland has the highest dementia mortality rate in the world. Scientists suspect that three main factors are at play, including a high prevalence of mycotoxin-producing indoor molds that thrive in the country’s damp, cold environment, high levels of neurotoxic mercury in seafood (a staple in the Finnish diet), and widespread selenium deficiency caused by selenium-poor soils. (25)
  5. Certain foods are significant sources of mycotoxins, particularly grains and meat and milk from grain-fed animals. The prevalence of mycotoxins in these foods provides all the more reason to eat an ancestral diet and be cognizant of food quality!