• According to a hypothesis put forward by some researchers, microbes in the soil and in the environment around us could be capable of influencing emotions.
• Through the gut-brain axis, they may modulate hormones such as dopamine, serotonin, and oxytocin.
• Further research is needed, but these findings could pave the way for microbiome-based strategies for mental health and relational wellbeing.

The microbes present in the soil and in the environments around us may influence the human microbiota and the gut-brain axis, potentially shaping emotional states and relational dynamics: this is a hypothesis being explored by biology researchers at Flinders University in Adelaide, Australia.

A review article published in a journal of the American Society for Microbiology synthesises the evidence that microbes can modulate key hormones and neurotransmitters such as dopamine, serotonin and oxytocin, and that the human gut microbiome could therefore influence the hormonal pathways involved in emotions associated with love, but also hatred and aggression.

Starting from microbes for new mental health strategies

"We are not claiming that microbes 'cause' love," said Jake Robinson, who leads the research. "Our goal is to map plausible biological pathways, grounded in microbiology and endocrinology, that researchers can now evaluate through rigorous human studies." If these pathways are confirmed, the findings could pave the way for microbiome-based strategies to support mental health and relational wellbeing. Further research is currently needed to unravel the extent to which microbiomes contribute to the neurobiology of emotions, and whether manipulation of microbial communities can modulate emotional and social behaviours.

The importance of soil in biological, environmental and social interactions

As part of the research, the scientists are also mapping the complex network of interactions between biological, environmental and social systems, focusing on the potential role in this network of the soil we come into contact with through the air we breathe, the food we eat, and the plants that surround us.

"In addition to emitting important chemical and microbial signals, healthy soils support vegetation that improves air quality, dampens noise and moderates temperature, creating immersive environments that influence our nervous, endocrine and immune systems," explained Martin Breed, one of the study's researchers. Conversely, as Breed also explains, soil degradation can increase harmful atmospheric particulate matter and reduce the richness of the aerobiome, with possible downstream effects on inflammation and mental wellbeing.