Evidence That the Gut Microbiome Is Linked to Major Depressive Disorder

Small studies have linked the gut microbiome to major depressive disorder (MDD), But they have been greeted skeptically — largely because the mechanisms by which bacteria in the gut might influence brain chemistry were obscure. To investigate this association further, a Chinese team studied 311 fecal samples from people with MDD and from healthy controls.

Forty-seven specific bacterial species, 3 specific bacteriophages, and 50 fecal metabolites were significantly associated with MDD. A combination of these biomarkers very accurately distinguished MDD from healthy controls in an independent set of fecal samples. Most important, the gut bacterial metabolites that correlated with MDD were molecules (e.g., γ-aminobutyrate, phenylalanine, trypto…