A recent study from the Institut Pasteur, Inserm and the CNRS revealed that an imbalance in gut bacteria can cause a reduction in some metabolites, resulting in depressive-like behaviors.
For the study, published in Nature Communications, the researchers studied the microbiotas of healthy animals and animals with mood disorders. They found that chronic stress caused changes to the gut microbiota, which therefore reduced the amount of lipid metabolites (or endocannabinoids) and lead to depressive symptoms.
"Surprisingly, simply transferring the microbiota from an animal with mood disorders to an animal in good health was enough to bring about biochemical changes and confer depressive-like behaviors in the latter," said Pierre-Marie Lledo, head of the Perception and Memory Unit at the Institut Pasteur.
The scientists identified some bacterial species that were significantly reduced in animals with mood disorders, and they note that these bacteria could potentially serve as an antidepressant (treatments called "psychobiotics").
"This discovery shows the role played by the gut microbiota in normal brain function," added Gérard Eberl, head of the Microenvironment and Immunity Unit (Institut Pasteur/Inserm). "If there is an imbalance in the gut bacterial community, some lipids that are vital for brain function disappear, encouraging the emergence of depressive-like behaviors. In this particular case, the use of specific bacteria could be a promising method for restoring a healthy microbiota and treating mood disorders more effectively."