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The Effect of Microbiome on Anxiety and Depression

Posted by Brad Dennis, Ph.D. on

The Effect of Microbiome on Anxiety and Depression

Bacteria are the new antibiotics, medical researches claim. Comfortably settled in for both their own and our organisms’ benefit, the good bacteria colonize almost every part of our bodies, thus forming a microscopically tiny ecosystem called the microbiome. Though most of the effects of the microbiome are well-known to laymen, a number of ground-breaking studies have now raised awareness of an interesting connection between the communities in our microbiome and our mental health.

Once done with testing, scientist will be able to provide yet another proof that gut health diet is a crucial aspect of every human organism, therefore hopefully uprooting our modern germophobia. More importantly, we’ll learn how to manipulate gut bacteria in a way most suitable to our overall well being, physical and psychological alike.

Here’s what they’ve established thus far.

The Yogurt Study

The primary function of both good and bad bacteria that reside within our gut is the absorption and digestion of nutrients; when balanced, this community – otherwise known as gut flora – vastly contributes to mechanisms triggered by our immune system, thus defending our body against diseases and retaining inner harmony. If imbalanced, the gut flora requires supplementary intake of good bacteria, most commonly found in natural probiotics such as yogurt.

There is no clearer symptom of impaired gut microbiome than a digestive issue, though doctors warn that brain-based problems like anxiety, depression and mood swings can come as a consequence of poor gut health as well. Though not entirely focused on mental disorders, the yogurt study conducted at U.C.L.A. proves that brain and gut are doubtlessly interconnected.

Over a course of one month, a woman received two portions of yogurt each day. Closely monitored, her brain functions revealed that good bacteria can indeed alter mental behaviour via the gut brain axis of the microbiome: instead of showing a typically anxious reflexive response to angry facial expressions, the woman stayed calm, “which shows that bacteria in our intestines really do affect how we interpret the world,” concludes the study's leader, Kirsten Tillisch.

Gut Bugs and Personality Disorders

Currently, that’s as far as researches are allowed to go when it comes to human subjects. Long before this study, however, the effects of microbiome on mental health were tested on mice and showed similar results.

The first, conducted over a decade in Japan, found the existence of a direct relationship between intestinal microbes and stress responses, while another one used both germ-free mice and people suffering from irritable bowel syndrome and anxiety as its possible side effect to successfully confirm the thesis that impaired gut flora triggers mental disorders.

The personality switch study, however, brings even more intriguing results. When taken from a naturally timid mouse and given to a naturally daring one, the gut bacteria alters the recipient’s behaviour by making it less shy and more exploratory, and vice versa. Conducted at McMaster University in Ontario, this research proved that microbiome influences personality disorders as well, which is yet another evidence of its connection to overall mental health, just as well as to anxiety and depression.

The Autism Connection

All this is to say that besides regulating digestive and immune system, the gut microbiota triggers changes in brain chemistry as well. So far, the studies demonstrated this thesis by observing stress responses, anxiety levels, depression causes and personality disorders. Now, scientists are going even further by exploring the role that our gut health diet potentially plays in autism patients.

Along with other common symptoms found in autistic children, gastrointestinal problems are very frequent as well. The fact that pregnancy fever increases chances for autism in yet unborn children by up to 7 times only stirred scientific curiosity more. Once noticed, this connection compelled researchers to investigate whether or not an imbalanced microbiome has anything to do with autistic behavior, and the results were more than astounding.

Once again, the test subjects were mice. This time, however, the study used a pregnant animal that was exposed to flu-like symptoms. Besides having displayed unquestionable signs of autism, the offspring had gastrointestinal issues as well, just like most human children born with this neuro-developmental disorder.

Can We Treat Mental Disorders with Healthy Microbiota?

What’s even more thought-provoking is the fact that the autistic mouse showed significant progress after being given the good bacteria as a treatment. Repetitive behavior, one of the regular symptoms of autism, was somewhat reduced, with the intestines almost fully regaining their proper function.

If healthy microbiota has the invaluable potential of restoring the well-being of autistic animals, then we can expect further research concerning medicinal uses of good bacteria on people. So far, they’ve been used as supplements that bring balance to the gut flora; in the future, they might be used as a cure for mental disorders.

As further proof of brain-gut axis, the autism study raised a couple of important questions. Obviously, this disorder is linked to intestinal microbiota, but is it possible that autism is actually reversible? Hopefully, we’ll have the answer in the near future.

Healthy Gut, Healthy Brain

Until then, scientists offer another explanation. The gut microbiome affects the human brain, and there’s no doubt about it any longer, but why and how it does that has been a mystery until recently. The findings from Northeastern University in Boston may hold the key.

According to their scientists, a newly discovered gut bacteria called KLE1738 cannot grow without GABA molecules. Being one of the most important elements for the brain’s chemical balance, GABA is directly linked to mental issues: its deficiency causes mood swings and depression.

In simple terms, but quite literally, bad gut bacteria feeds on our mental health, and GABA is probably not the only brain molecule on its menu. With that in mind, the importance of keeping them under control with healthy microbiota cannot be overstressed.

Ultimately, the repeatedly proven effect of microbiome on anxiety, depression and other mental disorders shouldn’t come as such a surprise. Though only human and despite their utter complexity, our bodies have been brought to perfection.

In order to function properly, though, they require inner balance, and the recently discovered brain-gut axis is only one of the mechanisms that ensures that. A healthy mind needs a healthy body, which is why the fact that a healthy psyche needs a healthy gut is perfectly understandable.


Mental Health May Depend on Creatures in the Gut 
Gaba Modulating Bacteria of the Human Gut Microbiome!/4060/presentation/18619
Melancholic microbes: a link between gut microbiota and depression?
Effects of intestinal microbiota on anxiety-like behavior


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