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Imbalance in Gut Microbiota Causes Depressive Behaviors in Rodent Study

January 06, 2021
microbiota graphic
CREDIT: Institut Pasteur / Pascal Marseaud

A stress-induced imbalance in gut microbiota caused a drop in lipid metabolites known as endogenous cannabinoids in the blood and brains of mice, and led to depressive-like behaviors in the animals, according to a study published in Nature Communications.

“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 study coauthor Pierre-Marie Lledo, PhD, head of the perception and memory unit at the Institut Pasteur, Paris, France.

Endogenous cannabinoids, or endocannabinoids, researchers explained, bind to receptors that are also the main target of THC, the active component of cannabis. An absence of endocannabinoids in the hippocampus, a brain region involved in memory and emotion, resulted in behaviors resembling depression.

Regulating Gut Bacteria May Ease Anxiety

The study also revealed which bacterial species were significantly reduced in mice with mood disorders. Oral treatment with the missing bacteria restored normal levels of lipid derivatives and alleviated depressive behaviors, reported researchers, who called the treatment approach “psychobiotic.”

“This discovery shows the role played by the gut microbiota in normal brain function,” said study coauthor Gérard Eberl, PhD, of Institut Pasteur. “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.”

—Jolynn Tumolo


Chevalier G, Siopi E, Guenin-Macé L, et al. Effect of gut microbiota on depressive-like behaviors in mice is mediated by the endocannabinoid system. Nature Communications. 2020;11(1):6363.

Gut microbiota plays a role in brain function and mood regulation [press release]. Paris, France: Institut Pasteur; December 9, 2020.

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