How Mould Might Reach the Brain, and Why the Toxins Are Not the Whole Story

Whether mould can genuinely affect thinking and mood has been contested for decades, largely because no controlled study had tested it directly or offered a credible mechanism. This experiment did both. Mice received measured intranasal doses of either intact toxic mould spores, the same spores chemically stripped of their toxins, or a saline control, repeatedly over five to six weeks. Both spore types reduced the birth of new hippocampal neurons and produced marked memory deficits in young mice, and the degree of immune activation in the hippocampus tracked the severity of the behavioural effects. The non-toxic spores also increased anxiety-like behaviour. The proposed explanation is innate immune activation rather than poisoning, which would make mould symptoms resemble those of a lingering infection. This is animal research and does not translate directly to human dose or experience, but it gives the long-reported symptoms a plausible biological route.