Research Suggests Association Between Gut Bacteria and Emotion

Summary: A new study identifies gut bacteria that appears to interact with brain areas associated with mood and behavior.

Source: UCLA.

Researchers have identified gut microbiota that interact with brain regions associated with mood and behavior. This may be the first time that behavioral and neurobiological differences associated with microbial composition in healthy humans have been identified.


Brain-gut-microbiota interactions may play an important role in human health and behavior. Previous research suggests that microbiota, a community of microorganisms in the gut, can influence behavior and emotion. Rodent models have demonstrated the effects of gut microbiota on emotional and social behaviors, such as anxiety and depression. There is, however, little evidence of this in humans.

For this study the researchers sought to identify brain and behavioral characteristics of healthy women clustered by gut microbiota profiles.


Forty women supplied fecal samples for profiling, and magnetic resonance images were taken of their brains as they viewed images of individuals, activities or things that evoked emotional responses. The women were divided by their gut bacteria composition into two groups: 33 had more of a bacterium called Bacteroides; the remaining seven had more of the Prevotella bacteria. The Bacteroides group showed greater thickness of the gray matter in the frontal cortex and insula, brain regions involved with complex processing of information. They also had larger volumes of the hippocampus, a region involved in memory processing. The Prevotella group, by contrast, showed more connections between emotional, attentional and sensory brain regions and lower brain volumes in several regions, such as the hippocampus. This group’s hippocampus was less active while the women were viewing negative images. They also rated higher levels of negative feelings such as anxiety, distress and irritability after looking at photos with negative images than did the Bacteroides group.

Image shows a drawing of the gut and bacteria.
Researchers do not yet know whether bacteria in the gut influence the development of the brain and its activity when unpleasant emotional content is encountered, or if existing differences in the brain influence the type of bacteria that reside in the gut. image is credited to NIH.


These results support the concept of brain-gut-microbiota interactions in healthy humans. Researchers do not yet know whether bacteria in the gut influence the development of the brain and its activity when unpleasant emotional content is encountered, or if existing differences in the brain influence the type of bacteria that reside in the gut. Both possibilities, however, could lead to important changes in how one thinks about human emotions.

About this neuroscience research article

Funding: This research was supported by grants from Danone Research and from the National Institutes of Health, including R01 DK048351, P50 DK64539, P30 DK041301 and R01 HD076756. In addition, pilot funds were provided for brain scanning by the Ahmanson-Lovelace Brain Mapping Center.

DISCLOSURE ​Tillisch received funding from Danone Research. Mayer is on the advisory boards for yogurt product company Dannon and its parent company Danone. Derrien, Le Nevé, Guyonnet and Brazeilles are or were employed by Danone Research at the time of the study. The remaining authors disclose no conflicts.

Source: Enrique Rivero – UCLA
Image Source: image is credited to NIH.
Original Research: The study will appear in Psychosomatic Medicine: Journal of Behavioral Medicine.

Cite This Article

[cbtabs][cbtab title=”MLA”]UCLA “Research Suggests Association Between Gut Bacteria and Emotion.” NeuroscienceNews. NeuroscienceNews, 30 June 2017.
<>.[/cbtab][cbtab title=”APA”]UCLA (2017, June 30). Research Suggests Association Between Gut Bacteria and Emotion. NeuroscienceNew. Retrieved June 30, 2017 from[/cbtab][cbtab title=”Chicago”]UCLA “Research Suggests Association Between Gut Bacteria and Emotion.” (accessed June 30, 2017).[/cbtab][/cbtabs]

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  1. This may well become the greatest understatement of the 21st century. “Both possibilities, however, could lead to important changes in how one thinks about human emotions.” Clearly if most if not all the conjectures and significant correlations are proved beyond reasonable doubt to be correct, bacterium controls to a degree our emotions and even the development of key executive cognitive brain structures and therefore their functionality and our emotional states – understanding humans cannot in essence survive without bacterium, humans become if not in part, in whole a vehicle for the continuing survival of bacterium.

    Discussion regards the existence of the soul becomes meaningless in fact dying from laughter would not in future be an unknown occurrence when someone detached from reality tries to argue the point. ‘Which soul the one we thought we had or the billions of souls that are parked in our living space pulling the strings?”

    Maybe René Descartes was right there’s body and mind (dualism), but rather than our body and mind-René Descartes Pineal gland-soul, mind-soul or simply mind (materialists) is our erstwhile bacterium inhabiting our guts whose origin is as ours determined by our mothers at birth, they come along for the ride, or is it us coming along for the ride?

    Free-will although suspect before may be becoming more so. Whose mind, as we are not alone, we are walking environments the members of which appear at first glance to possibly have significant input into who we think we are, how we feel emotionally and given the correlation with the hippocampus what we may end up knowing or not knowing.

    Or maybe this research is just another set of significant correlations which in reality have no connection-I feel much better-though I must urgently check which bacterium are the majority in residence as I require a fair bit more body in the frontal cortex, insula, and hippocampus brain regions.

    Given the possible cognitive-emotional effect of gut bacterium maybe some biological psychologist should start a research project to ascertain if in some way the propensity of those undergoing stomach reduction, bypassing, etc. to suicide, being as it is four times that of the general population has something to do with altered messaging either through altered states of bacterium or their messaging connections to other parts of the body, and also investigate what the changes in gut environment-structure may have on subsequent cognitive-emotional issues and why this may be or may not be so. Plus knowing the integral part bacterium takes in our immune system whether or not those undergoing stomach operations become more or less susceptible to immune deficiency effects i.e. at least the relative probability of ending up with the flue/cold compared to the general population.

    One would possibly expect some kind of adjustment with the body and/or bacterium seeking previous equilibrium states which may have been made impossible by the type of and/or extent of the surgery.

    Given the possible link to relative size of executive brain structures it may turn out to be advisable at or shortly after birth to perform a fecal microbiota transplant or more preferably for mothers to make sure the most advantageous bacterium crosses with the child.

    This research needs replicating with a larger sample longitudinal study and those having stomach surgery may be a good group to include and evaluate before and after surgery.

    It appears the Greeks rather than René Descartes may have been right the human within ‘gastric centers reside basic soul expression, attributes of passion, fight (emotionally driven behavior) and drive (executive function).’

    Scifi possibly, but yes I agree research in this area “could lead to important changes in how one thinks about human emotions.” and possibly a few other human myths we have created.

  2. Which came first? The chicken or the egg? It does show that probiotics are important for our emotional and physical health. Just make sure it is a good one. Better to pay a bit more and get quality. Be all over healthy and enjoy life. I love that it will be published in Psychosomatic Medicine. For 35 years I was told my health problems were in my head BY NEUROLOGISTS as well as regular doctors. I didn’t see a doctor for 20 years. Then just before I completely quit breathing because my autonomic nervous system was giving up the fight they found the problem. It was ALL IN MY HEAD. I had a brain/cervical procedure for the Chiari Malformation I’d been born with.

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