Research into the gut microbiome has accelerated dramatically over the past decade, revealing that the trillions of microorganisms inhabiting the human digestive tract produce neurotransmitters, regulate inflammation, and communicate with the brain through the vagus nerve in ways that directly influence mood, cognition, and stress responses. Individuals with depression, anxiety, and autism spectrum disorder have consistently shown altered microbiome composition compared to neurotypical controls.
Clinical application remains in early stages. Probiotic interventions have shown modest effects on anxiety and depressive symptoms in several randomized trials, but the optimal strains, doses, and populations have not been established. Fecal microbiota transplantation has demonstrated dramatic efficacy for recurrent Clostridioides difficile infection and is being explored for psychiatric and neurological conditions in early clinical trials. The field faces the fundamental challenge that each person's microbiome is unique.
