The Role of the Gut Microbiota in Mood and Behavior

By Hunna Watson, Camden Matherne, and Susan Kleiman
Published: March 2, 2015

“Just go with your gut,” and “I’ve got a gut feeling,” are phrases that have been around for decades. In light of this long-standing recognition that our gut may impact how we feel and behave, thanks to cutting-edge research, we are beginning to uncover the science behind this phenomenon.

Your gut is home to the intestinal microbiota, a thriving, vibrant powerhouse that is critical for human survival. The NIH Human Microbiome Project, initiated in 2007 and completed in 2012, is contributing to our understanding of the role of the microbiome in human health and diseases. Our microbiomes develop primarily during the first three years of life, and are highly individualized, based on myriad environmental influences such as whether we are breast- or formula-fed as a baby and where we live. In terms of maintaining our health, bacteria and other microbes play an essential role, from extracting nutrients from the food we eat to bolstering our immune system.

Our brain, as part of the central nervous system, impacts our gut. This relationship explains why some people get “butterflies in the tummy” before a big presentation or lose their appetite in a crisis. Of great interest to the mental health field is new research suggesting that this relationship is bidirectional – our gut appears to influence our emotions and behavior and has recently been called our “second brain.” In support of this idea, research with animals has revealed that the gut microbiota impacts how strongly we react when stressed. In addition, altering the microbiota of mice results in changes in anxiety- and depressive-like behaviors.

What about human research, you might ask? Only limited studies thus far have been conducted with humans. Healthy adults and adults with chronic fatigue syndrome report less feelings of stress after taking a probiotic for a period of time, compared to similar adults who don’t take a probiotic. Altogether, this research has led scientists to believe that our gut microbiota could play a role in causing or maintaining mental health problems.

Specific to the eating disorders field, scientists have uncovered that, in response to a number of stressors, such as infection, stress, or dietary changes, our gut can directly impact areas of the brain that impact appetite and mood. The microbiota may also affect how efficiently our bodies extract calories from the food we eat. Research in Science showed that mice who received a microbiota transplant from an obese human gained more weight than those who received a transplant from a lean human.

This research highlighting the role of the gut in mood, behavior, and energy balance suggests that the gut may have a role in the development and maintenance of eating disorders. However, new and safe treatment approaches targeting our microbiome have yet to be uncovered. Stay tuned!


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photo credit: Immune Cells Surrounding Hair Follicles in Mouse Skin via Creative Commons