Human Threat Learning is Associated with Gut Microbiota Composition

Rodent studies have shown that the gut microbiota can influence threat and safety learning, which has been linked to anxiety phenotypes. In humans, it has been demonstrated that microbiota composition varies with anxiety disorders, but evidence showing an association with threat learning is lacking. Here, we tested whether individual variability in threat and safety learning was related to gut microbiota composition in healthy adults. We found that threat, but not safety learning varies with individuals’ microbiome composition. Our results provide evidence that the gut microbiota is associated with excitatory threat learning across species. Significance Statement Learning from threats and safety is a core mechanism of anxiety disorders, and studies in rodent models have shown that the gut microbiota can modulate such behaviors. Although previous literature on humans shows a relationship between emotional circuits and gut microbiota, the evidence linking learning and microbiota is lacking. In a Pavlovian threat conditioning paradigm, we show that patterns of gut microbiota composition in healthy humans relate to their patterns of threat learning, but not safety learning. Our findings suggest one mechanism by which the human gut microbiota is associated with anxiety-related behaviors. ### Competing Interest Statement The authors have declared no competing interest.