The Gut–Brain Axis in Depression: Genetic, Immunological, and Microbiota-Based Evidence

This preprint presents a narrative review exploring the role of the gut–brain axis in depression, integrating genetic, immunological, and microbiota-based evidence. The manuscript discusses emerging biological mechanisms linking intestinal function, immune activation, and neuroplasticity to depressive disorders, highlighting depression as a systemic condition involving dynamic interactions between the gut, immune system, and brain. This work is intended for scientific discussion and interdisciplinary dissemination and has not undergone peer review.