New research shows probiotics can help relieve depression

Good bacteria to fight depression

The gut microbiome plays an important role in health, including mental health. Researchers from the University of Basel and the University Psychiatric Clinics Basel (UPK) have shown that probiotics can enhance the effect of antidepressants and help relieve depression.

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

What may come as a surprise to many is that scientists have just discovered that your gut flora, the trillions of bacteria and other microbes that live in your digestive tract, can affect depression. Still, it’s not as strange as it sounds, as your gut microbiome is known to play an important role in health and may have links to weight loss, autism, COVID-19 severity, ALS and drug safety and effectiveness.

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

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

One promising approach is the microbiome-gut-brain axis. By microbiome, we generally mean all the microorganisms that live in or on the human body, such as the intestinal flora. Intestinal bacteria can influence the nervous system, for example 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 on June 3, 2022 in the journal 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 a higher than average prevalence of intestinal and digestive problems. If the intestinal flora of people suffering from depression is implanted in mice raised under sterile conditions, that is to say without intestinal flora, the animals also develop depressive-like behavior. For example, they are less energetic and less interested in their surroundings than their peers. The researchers therefore suspect that the composition of the bacterial community in the intestine plays an important role in depressive symptoms.

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

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

Subsequent analysis showed that although depressive symptoms decreased in all participants with systemic antidepressant treatment, there was greater improvement in subjects in the probiotic group than in the placebo group.

In addition, the composition of their intestinal flora changed, at least temporarily: in the probiotic group, an analysis of stool samples revealed an increase in 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 declined again over the next four weeks. “It may be that four weeks of treatment is not long enough and that it may take longer for the new composition of the intestinal flora to stabilize”, explains Anna-Chiara Schaub, one of the main authors of the study.

Change in the processing of emotional stimuli

Another interesting effect of taking probiotics was observed in relation to brain activity when viewing neutral or fearful faces. The researchers studied this effect using functional magnetic resonance imaging (fMRI). In patients with depression, certain regions of the brain for emotional processing behave differently than in mentally healthy people. 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 several years, the exact mechanisms have yet to be fully clarified,” says Schaub. This is another reason why researchers felt it was important to use a wide range of bacteria in the form of probiotics, such as the 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 use the best mix in order to support the treatment of depression”, explains the researcher – even if she holds to point out 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 control trial” by Anna-Chiara Schaub, Else Schneider, Jorge F. Vazquez-Castellanos, Nina Schweinfurth, Cedric Kettelhack, Jessica PK Doll, Gulnara Yamanbaeva, Laura Mählmann, Serge Brand, Christoph Beglinger, Stefan Borgwardt, Jeroen Raes, André Schmidt and Undine E. Lang, June 3, 2022, Translational psychiatry.
DOI: 10.1038/s41398-022-01977-z

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