We’ve seen a dramatic rise in stress, anxiety, and depression in recent years (World Health Organization, 2023). Although the authoritative Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 2013) lists symptoms of anxiety and depression, it fails to address one key factor: the relationship between our brain and our gut—or specifically, our gut microbiome, the trillions of bacteria, fungi, protozoa, and viruses that live within our digestive system.

Yet research has found that our gastrointestinal tract contains over one hundred trillion microorganisms essential to our emotional and physical health (Rieder and colleagues 2017). The gut microbiome is connected to our brain function by the gut-brain axis, an internal, bidirectional pathway between the gut and the brain via the vagus nerve. Research has shown that this complex communication system not only influences intestinal activities like digestion and motility, but also helps regulate our immune and pain response system, metabolism, mood, social behavior, and cognition.

To find out more about the powerful connection between the microbiome and our mental health, I talked to Raja Dhir, co-founder of Seed Health, which brings together international researchers to find science-based microbial solutions for personal and planetary health. Dhir is deeply committed to conservation on many levels. He works to protect our marine environment and the vulnerable honeybee populations as well as to help us maintain our ecosystems, including the community of microbes that support the life within us.

Dhir explains that we have microbiomes in many areas of the body including the skin, mouth, and genitals. He works with scientists from major universities to study how these microorganisms affect our mood,........

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