The Second Brain: Understanding the Role of Gut Microbiome in Depression

The gut microbiome (enterobiome) has emerged as a key regulator of the gut–brain axis, influencing mental health through neural, immune, endocrine, and metabolic pathways(3,4,5). Increasing evidence suggests that gut dysbiosis is closely associated with Major Depressive Disorder (MDD)(1,3,11) , contributing to chronic inflammation, altered neurotransmitter synthesis, impaired intestinal barrier function, and hypothalamic–pituitary–adrenal (HPA) axis dysregulation (2,20) . Depression and gut microbiome alterations appear to share a bidirectional relationship, with each capable of exacerbating the other. Experimental and clinical studies support the role of microbial imbalance in depressive symptoms, highlighting the therapeutic potential of microbiota-targeted interventions, including dietary modification, probiotics, prebiotics, symbiotics, postbiotics, and faecal microbiota transplantation as adjunctive treatments(25,26,30). We explore the relationship between the gut microbiome and mental health with special emphasis on the role in depression.