Can Gut Bacteria Cure Depression?

gut bacteria
Written by David Tuttle

It has long been known that gut bacteria play a pivotal role in digestive health, but what about its effect on mental health? Could something as elemental as the microbiome of a person’s gastrointestinal tract possibly lead to depression, bipolar disorder and even schizophrenia? And if the gut were treated, could those mental health issues be helped?

Well, to put it simply, yes — but it’s not that simple.

The importance of our gut bacteria

The human gut flora is comprised of around 1,000 different species of bacteria — and even more unique strains contained within those species — creating a very diverse environment inside the human body. While these microscopic organisms’ main role is to ensure a healthy digestive system and to strike a somewhat lopsided balance between good and bad bacteria, scientists have linked them to a number of additional roles regarding a person’s health.

When specifically looking at mental health, gut microbiota’s importance becomes much clearer. The stress hormone cortisol, which is often found in excess in the body when a person experiences anxiety, is governed by the hypothalamic-pituitary-adrenal axis — one of the brain’s regulatory systems for the stress response. The pathway by which bacteria in your gut can manipulate this system is still not entirely understood; however, it is suspected that components of the bacterial cell wall cause an inflammatory response and the release of inflammatory proteins called cytokines. These cytokines then trigger an immune response as well as signal to the hypothalamic-pituitary-adrenal axis to release cortisol.

This perverse interaction promotes the release of cortisol in times where an anxiety response is not warranted or could increase the severity of the anxiety response. The influence of the gut bacteria in the release of cortisol, combined with their role in releasing the inflammatory cytokines — which can lead to gastrointestinal pain — could mean that an imbalanced gut microbiota acts as potentially both the cause and the effect of certain mental disorders.

Treating the gut with the mind

Research studies have demonstrated that patients with gastrointestinal issues benefit greatly from therapy and from utilizing coping mechanisms that are often suggested by psychologists as treatments for depression and anxiety. By incorporating tactics such as mindful meditation, yoga and acceptance therapy into treatment, a person with a gastrointestinal condition could improve their aliment by simply using their mind. This research further supports the notion that a person’s mind is a powerful entity and is directly correlated with certain physical conditions, especially those in the gut.

So, if methods for treating mental health can be used for gastrointestinal diseases, why shouldn’t the reverse also be true? The exact composition of a person’s gut microbiota, not just an imbalance, has been discovered to contribute to mental health issues as well.

Promising research into gut bacteria

A 2019 study showed that two types of bacteria, coprococcus and dialister, are found in greater quantities in people without depression. Additionally, certain subsets of bacteria, mainly veillonellaceae and lachnospiraceae, have been discovered to cause negative behavioral changes in mice when transplanted from schizophrenia patients into healthy mice.

This research is very recent, still without similar experiments to try to replicate the results of these studies. But if they, too, find these certain bacteria are linked to depression and schizophrenia, that would be a significant development in mental health research, as a new physical link would have been uncovered. The presence or absence of coprococcus, dialister, veillonellaceae and lachnospiraceae has a potentially potent effect on a person’s mental health, warranting further research on the topic so that a specific treatment plan for these mental illnesses can be devised using these bacteria.

Given all of this, what can one do to promote a healthy, diverse gut microbiome and a healthy mind? Short of a fecal transplant from a person without anxiety or depression, one can still attempt to foster a healthy gut-brain connection in a variety of ways.

How to keep your gut healthy

First and foremost is a healthy diet that is low in fat. Studies show that while a high fat diet in mice leads to depression, anxiety and obsessive-compulsive behaviors, these effects can be reversed if the gut microbiome is altered. This can be done by incorporating a healthier diet and adding probiotics or even antibiotics, although caution should be used with antibiotics, which will essentially reset your gut microbiota by eradicating most bacteria in your gut, both good and bad.

Fermented foods such as yogurt and pickles often have the necessary probiotics for a healthy digestive system, so adding these to your diet could potentially improve your own mental health. Another option is omega-3 supplements, which have been linked to both improving the diversity of the gut microbiome as well as reducing the amount of inflammatory cytokines released, possibly due to the presence of a metabolite that reduces oxidative stress in the gut, promoting growth of healthy bacteria.

Treating mental health

While there is a growing body of research to confirm the fascinating link between the gut and brain, this information should be taken with a proverbial grain of salt.  Eating more yogurt is not the be-all-end-all cure for depression or schizophrenia. Maintaining a healthy gut microbiome is merely an additional avenue to attempt to treat mental illness. It is still important to treat mental health by practicing techniques such as mindfulness or regular exercise and by seeing a professional.

In conjunction with therapy and antidepressant medication, improving one’s gut microbiota health has the potential to improve some people’s mental health and help psychologists further understand this seemingly bizarre yet necessary, gut-brain connection.

In addition to depression, anxiety, and schizophrenia, gut bacteria have been found to relieve symptoms of autism in a paper published in 2018. A study of 18 autistic children with gastrointestinal issues, a common pairing for autism, found that fecal transplants from non autistic individuals lessened the severity of both their gastrointestinal problems and some symptoms of autism such as hyperactivity and irritability.  These improvements were found to be sustained even two years after the transplant during a follow up experiment.  The study found that the bacteria, Prevotella, was found in much higher concentrations post fecal transplant as well as two years after the procedure.  This paves the way for exciting research and treatment opportunities to treat a disorder that was once thought to be entirely in the mind but is now shown to have an important connection to the gut.

About the author

David Tuttle

David Tuttle is a bench scientist in the Pharmaceutical industry working on vaccines and cell culture. He has his B.S in Biology from the University of Richmond and currently resides in Richmond V.A. with his dog, Sandwich.

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