Journal of psychiatric researchMar 31, 2019

Differences in Gut Bacteria in Major Depression Compared to Bipolar Disorder with Current Depressive Episodes

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Updated Mar 31, 2026

Abstract

The Gcoefficients are significantly decreased in both major depressive disorder (MDD) and bipolar disorder (BPD) groups.

MDD and BPD patients showed significant increases in the phyla Firmicutes and Actinobacteria, along with a significant decrease in Bacteroidetes compared to healthy controls.
Four out of the top five enriched genera in MDD and BPD patients were Bacteroides, Clostridium, Bifidobacterium, and Oscillibacter, indicating notable shifts in gut microbiota.
Escherichia and Klebsiella genera showed significant changes only between BPD patients and healthy controls.
MDD patients exhibited a higher abundance of several Prevotella species compared to BPD patients.
In BPD patients, the abundance of certain bacteria, including Fusobacteriaceae and Klebsiella oxytoca, was significantly increased, while Bifidobacterium longum was significantly reduced compared to MDD patients.

Simplified

BACKGROUND: To probe the differences of gut microbiota among major depressive disorder (MDD), bipolar disorder with current major depressive episode (BPD) and health participants.

METHODS: Thirty one MDD patients, thirty BPD patients, and thirty healthy controls (HCs) were recruited. All the faecal samples were analyzed by shotgun metagenomics sequencing. Except for routine analyses of alpha diversity, we specially designed a new indicator, the Gcoefficient, to evaluate the inequality of relative abundances of microbiota for each participant. m

RESULTS: The Gcoefficients are significant decreased in both MDD and BPD groups. The relative abundances of increased phyla Firmicutes and Actinobacteria and decreased Bacteroidetes were significantly in the MDD and BPD groups. At genus level, four of top five enriched genera (Bacteroides, Clostridium, Bifidobacterium, Oscillibacter and Streptococcus) were found increased significantly in the MDD and BPD groups compared with HCs. The genera Escherichia and Klebsiella showed significant changes in abundances only between the BPD and HC groups. At the species level, compared with BPD patients, MDD patients had a higher abundance of Prevotellaceae including Prevotella denticola F0289, Prevotella intermedia 17, Prevotella ruminicola, and Prevotella intermedia. Furthermore, the abundance of Fusobacteriaceae, Escherichia blattae DSM 4481 and Klebsiella oxytoca were significantly increased, whereas the Bifidobacterium longum subsp. infantis ATCC 15697 = JCM 1222 was significantly reduced in BPD group compared with MDD group. m

CONCLUSIONS: Our study suggested that gut microbiota may be involved in the pathogenesis of both MDD and BPD patients, and the nuances of bacteria may have the potentiality of being the biomarkers of MDD and BPD.

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Differences in Gut Bacteria in Major Depression Compared to Bipolar Disorder with Current Depressive Episodes

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