New research shows probiotics may help relieve depression

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Probiotic Supplements

Good bacteria to fight depression

The gut microbiome plays an important role in health—including mental health. Researchers at the University of Basel and the University Psychiatric Clinics Basel (UPK) have shown that probiotics support the effects of antidepressants and can help alleviate depression.

In modern society, depression is a fairly common problem. In fact, according to the CDC, 18.5% of adults surveyed in the United States in 2019 had symptoms of depression that were either mild, moderate, or severe in the past 2 weeks.

What may surprise many is that scientists have just found that your gut flora, the trillions of bacteria and other microbes that live in your digestive tract, can affect depression. This isn’t as strange as it sounds, however, as your gut microbiome is known to play a significant role in health and may be linked to weight loss, autism, the severity of COVID-19, ALS, and drug safety and efficacy.

When visited by what he dubbed “the black dog,” Winston Churchill could barely get out of bed. He had no energy, no interests, and no appetite. Although the British Prime Minister did not invent this metaphor for depression, he was the one who popularized it.

Experts try drugs and psychotherapy to help patients escape the “black dog,” but for some people it persists. Researchers are therefore looking for ways to improve existing therapies and develop new ones.

A promising approach is the microbiome-gut-brain axis. The microbiome is generally understood to mean all microorganisms that live in or on the human body, such as the intestinal flora. Intestinal bacteria can, for example, influence the nervous system via metabolic products.

In a recent study, a research team from the University of Basel and the University Psychiatric Clinics Basel (UPK) showed that probiotics can support treatment with antidepressants. They reported their findings in the journal on June 3, 2022 Translational Psychiatry.

Illustration of the human gut microbiome

Illustration of the human gut microbiome.

The intestinal flora influences the psyche

It is known from previous studies that patients with depression have an above-average frequency of intestinal and digestive problems. If the intestinal flora of people with depression is transplanted into mice that have been reared sterilely, i.e. without intestinal flora, the animals will also develop depressive behavior. For example, they are less energetic and show less interest in their surroundings than their peers. Researchers therefore suspect that the composition of the bacterial community in the gut plays an important role in depressive symptoms.

“With additional knowledge of the specific effects of certain bacteria, it may be possible to optimize bacterial selection and use the best mix to aid in the treatment of depression.” Anna Chiara Schaub

In their new study, researchers led by Dr. André Schmidt and Professor Undine Lang systematically examine the effects of probiotics on patients with depression. All participants were inpatients at the University Psychiatric Clinics in Basel (UPK) and received antidepressants, a probiotic (21 subjects) or a placebo (26 subjects) for 31 days. Neither the participants nor the study staff knew which preparation the subjects were taking during the entire study period. The researchers performed a series of tests on the participants immediately before treatment, at the end of 31 days and again four weeks later.

Subsequent analysis showed that while depressive symptoms decreased in all participants thanks to general antidepressant treatment, the probiotics group improved more than the placebo group.

In addition, the composition of their intestinal flora changed, at least temporarily: In the probiotics group, an analysis of stool samples showed an increase in lactic acid[{” attribute=””>acid bacteria at the end of treatment – an effect that was accompanied by a reduction in depressive symptoms. However, the level of these health-promoting gut bacteria decreased again over the following four weeks. “It may be that four weeks of treatment is not long enough and that it takes longer for the new composition of the intestinal flora to stabilize,” explains Anna-Chiara Schaub, one of the lead authors of the study.

Change in the processing of emotional stimuli

Another interesting effect of taking probiotics was seen in relation to brain activity when viewing neutral or fearful faces. The researchers investigated this effect using functional magnetic resonance imaging (fMRI). In patients with depression, certain brain regions for emotional processing behave differently than in individuals with good mental health. After four weeks of probiotics, this brain activity normalized in the probiotic group but not in the placebo group.

“Although the microbiome-gut-brain axis has been the subject of research for a number of years, the exact mechanisms are yet to be fully clarified,” says Schaub. This was another reason why the researchers believed it was important to use a wide range of bacteria in the form of probiotics, such as formulations already available on the market. “With additional knowledge of the specific effect of certain bacteria, it may be possible to optimize the selection of bacteria and to use the best mix in order to support treatment for depression,” says the researcher – although she is keen to emphasize that probiotics are not suitable as a sole treatment for depression.

Reference: “Clinical, gut microbial and neural effects of a probiotic add-on therapy in depressed patients: a randomized controlled trial” by Anna-Chiara Schaub, Else Schneider, Jorge F. Vazquez-Castellanos, Nina Schweinfurth, Cedric Kettelhack, Jessica P. K. Doll, Gulnara Yamanbaeva, Laura Mählmann, Serge Brand, Christoph Beglinger, Stefan Borgwardt, Jeroen Raes, André Schmidt and Undine E. Lang, 3 June 2022, Translational Psychiatry.
DOI: 10.1038/s41398-022-01977-z

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