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New Study: Gut Bacteria Linked to Depression

New Study: Gut Bacteria Linked to Depression
March 15
11:00 2016

What scientists refer to as “gut microbiota” is a massive amount of genetic material contained in the digestive tubes of animals and humans. Add up these trillions of microbes and you get what scientists call the “microbiome,” which can be viewed as a sort of organ that modern science does not fully understand. Although we already knew about the link between mood and gut bacteria, a new study sheds some light on the correlation between microbes and depression.

“We are, at least from the standpoint of DNA, more microbial than human. That’s a phenomenal insight and one that we have to take seriously when we think about human development,” explains Tom Insel of the National Institute of Mental Health. He believes the “sense of self” is directly related to microbial activity. 

Mark Lyte, a researcher at Texas Tech University, has spent most of his career attempting to prove that gut microbes “talk” to the nervous system using the same neurochemicals that relay messages within the brain.

Lyte made significant progress last year studying monkey feces. “You wouldn’t believe what we’re extracting out of poop!” he told the NY Times. “We found that the guys here in the gut make neurochemicals. We didn’t know that. Now, if they make this stuff here, does it have an influence there? Guess what? We make the same stuff. Maybe all this communication has an influence on our behavior.”

Gut bacteria has already been linked to inflammatory bowel disease, obesity, and toxic side effects of some medications. More interesting to Lyte and fellow researchers is the fact that gastrointestinal abnormalities have been linked to autism, hyperactivity, anxiety, and depression.

A field that has long struggled to attract money and scientific credibility is now soaring with discoveries. In 2014, the National Institute of Mental Health gave out four grants of $1 million each to researchers looking into the role gut microbiomes may play in mental disorders. Lyte and his fellow researchers received one of the grants.


1432659062dca0ac1aDepression is a chronic mood disorder that currently affects 19 million Americans. It is linked to various biological, genetic, and environmental factors. Depression affects how you think feel, and behave and can lead to a host of physical and emotional problems.

Major Depressive Disorder (MDD) is defined as a mental disorder characterized by consistent low mood, low self-esteem, loss of interest, and inability to feel pleasure. MDD is a disabling condition that causes nearly 4% of victims to take their own lives.

While multiple links between gut microbiota and depression have been found in animals, little correlation has been observed in humans – until now.

Last year, a group of Chinese researchers took fecal samples from 46 individuals suffering from MDD and compared it to fecal samples from 30 healthy adults. The goal was to discover if depression has an affect on the stability of gut microbiota.

Through high-throughput pyrosequencing, researchers found a much higher level of Bacteroidetes, Proteobacteria, and Actinobacteria in the fecal matter of the depressed group than in the healthy group.

While individual levels varied, there were several noticeable differences between the genera of the two groups. The MDD group had a higher level of Enterobacteriaceae and Alistipes, but a lower level of Faecalibacterium than the healthy group. There was a negative correlation between Faecalibacterium and severity of depression.

These findings provide a better understanding of the changes in gut microbiota composition in depressed patients, showing either a prevalence of harmful bacteria or lack of beneficial bacteria (download the full study here).

Although more studies are needed to discover the precise relationships between gut bacteria and MDD, this study provides a great start. Furthermore, the prediction that we may in the future use microbes to diagnose and treat disorders has become plausible.




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April Kuhlman

April Kuhlman

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