How does the gut-brain axis influence mental health?

The answer

The gut-brain axis is a bidirectional communication network linking the enteric nervous system's 500 million neurons with the brain via the vagus nerve, immune signaling, and microbial metabolites. A landmark 2019 study in Nature Microbiology analyzing over 1,000 participants found that specific gut bacteria - Coprococcus and Dialister - were consistently depleted in people with depression. Gut microbes produce approximately 95% of the body's serotonin and 50% of its dopamine. In 2024, clinical trials showed that specific probiotic strains (Lactobacillus and Bifidobacterium) reduced depression scores by 40% in mild-to-moderate cases. Fecal transplants are now being investigated as treatment for treatment-resistant depression.