Mould and your mind: the research on brain fog, anxiety and depression
by Kath P on May 28, 2026
If you've been living with unexplained fatigue, a persistent foggy feeling, low mood or anxiety that doesn't quite fit anything else, your indoor environment might be worth a look. The link between mould exposure and mental health is one of the more surprising chapters in the indoor air quality literature — and it's one that's been building for years.
What people living in mouldy buildings actually report
The symptom picture isn't subtle. People working or living in mould-affected buildings consistently report a cluster that goes well beyond sneezing: fatigue, pain, increased anxiety, depression, difficulty concentrating, and what has come to be called brain fog — a slow, foggy, disconnected feeling that makes it hard to think clearly or stay on task. A 2021 review confirmed this pattern, and in 2024 the Association of Scientific Medical Societies in Germany (AWMF) updated its clinical guidance to formally recognise mood disorders as a potential symptom of mould exposure.
The animal research that proposed a mechanism
Animal studies have been critical here because they allow researchers to test mould exposure directly and observe the effects on brain function. A 2014 study published in Brain, Behavior, and Immunity exposed mice to spores of Stachybotrys chartarum — one of the most studied indoor moulds — and found significant memory deficits on contextual memory tasks, increased anxiety, and elevated levels of inflammation-related cells in the hippocampus. The researchers concluded that respiratory exposure to mould, not just the particularly toxic varieties, may be capable of causing brain inflammation, cognitive deficits and emotional problems.
A 2021 animal study went further, finding that mould inhalation appeared to trigger an innate immune response that led to problems with memory and anxiety symptoms — the same immune-activation pathway implicated in the cognitive effects of viral and bacterial illness.
The older adults study: 11,000 participants
A 2024 study drawing on data from over 11,000 adults aged 65 and older (the Chinese Longitudinal Healthy Longevity Survey) found that mould exposure was significantly associated with increased anxiety symptoms — almost doubling the odds compared with non-exposed individuals. Cognitive impairment partially mediated the relationship, meaning part of the pathway from mould to anxiety ran through cognitive decline. Importantly, two protective factors were identified: open window ventilation and multivitamin supplementation. Both meaningfully reduced the strength of the association.
Depression: what a large European study found
A multi-country European population study found that people living in homes with mould had significantly higher odds of depression, even after controlling for other variables. The researchers found the heightened depression risk was partly explained by physical health problems linked to mould, and partly by a sense of helplessness — a feeling that the damp, mouldy environment couldn't be controlled. It's a useful finding: the mental health burden of mould isn't just biological. The chronic stress of living in an environment you can't fix is its own weight.
How the biology is thought to work
The proposed mechanisms aren't mysterious. Chronic mould exposure can trigger ongoing low-level inflammation — the same inflammatory pathway that has been repeatedly linked to depression and cognitive impairment in other contexts. Mycotoxins, the toxic compounds some moulds produce, have been shown in research to potentially disrupt blood-brain barrier function and interfere with neurotransmitter systems. Whether this translates cleanly from laboratory findings to lived experience in a typical home remains an active area of research, but the direction of evidence is consistent.
What to do with this information
If you're experiencing a combination of respiratory symptoms and any of the cognitive or mood effects described above — particularly in a home you know has dampness issues — it's worth raising with a GP who is familiar with environmental health factors. And it's worth addressing the environment itself. The solution isn't complicated: control the moisture, reduce the mould, improve the air.
Clearer air, clearer head
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About the author: Kath P is a writer and researcher covering indoor mould, humidity and environmental health at The Dew. Journal. Her work draws on WHO guidelines, peer-reviewed research and the real-world experiences of Australian homeowners and renters.
