Correlation between the human fecal microbiota and depression

Abstract Background Depression is a chronic syndrome with a pathogenesis linked to various genetic, biological, and environmental factors. Several links between gut microbiota and depression have been established in animal models. In humans, however, few correlations have yet been demonstrated. The aim of our work was therefore to identify potential correlations between human fecal microbiota (as a proxy for gut microbiota) and depression. Methods We analyzed fecal samples from 55 people, 37 patients, and 18 non‐depressed controls. Our analyses were based on data generated by Illumina deep sequencing of 16S r RNA gene amplicons. Key Results We found several correlations between depression and fecal microbiota. The correlations, however, showed opposite directions even for closely related Operational Taxonomic Units ( OTU 's), but were still associated with certain higher order phylogroups. The order B acteroidales showed an overrepresentation ( p = 0.05), while the family L achnospiraceae showed an underrepresentation ( p = 0.02) of OTU 's associated with depression. At low taxonomic levels, there was one clade consisting of five OTU 's within the genus O scillibacter , and one clade within A listipes (consisting of four OTU 's) that showed a significant association with depression ( p = 0.03 and 0.01, respectively). Conclusions & Inferences The O scillibacter type strain has valeric acid as its main metabolic end product, a homolog of neurotransmitter GABA, while A listipes has previously been shown to be associated with induced stress in mice. In conclusion, the taxonomic correlations detected here may therefore correspond to mechanistic models.