The Gut Microbiome Might Play a Role in Depressive Illness

Gut microbiota influence brain function and behavior in animals, and preliminary studies have shown differences in composition of gut microbiota between depressed and euthymic patients. In this series of studies, germ-free mice (i.e., having no gut microbiome) were protected from the depression-like immobility during the forced swimming test and the anxiety behaviors on the Y-maze test that healthy mice suffered when exposed to these tests. Stool samples from 58 Han Chinese patients with major depression and 63 healthy, nonpsychiatric controls showed distinct differences in depressed patients' microbiome with altered amounts of species from three bacterial phyla (Firmicutes, Actinobacteria, and Bacteroidetes). Transplantation of fecal sampl…