The intestinal flora plays an important role in health, including mental health. Researchers at the University of Basel and the University Psychiatric Clinics of Basel, Switzerland, have shown that probiotics can enhance the effect of antidepressants and help alleviate depression.
Sir Winston Churchill, when visited by what he called “the black dog”, could hardly get out of bed. He had no energy, no interests, and no appetite, among other symptoms. Although the British Prime Minister did not invent this metaphor for depression, he was the one who popularized it. Experts use medication and psychotherapy to try to help patients escape the “black dog,” but it persists in some people. Therefore, researchers are looking for ways to improve existing therapies and develop new ones.
One promising approach is the microbiome-gut-brain axis. Microbiome refers to the set of microorganisms that live in or on the human body, such as intestinal flora. Gut bacteria can influence the nervous system, for example through metabolic products.
In the study, published in the scientific journal ‘Translational Psychiatry’, these Swiss scientists have shown that probiotics can support treatment with antidepressants. It is known from previous studies that depressed patients show a higher than average prevalence of bowel and digestive problems. If the intestinal flora of people with depression is implanted in mice raised in sterile conditions (ie, without intestinal flora), the animals also develop depression-like behavior. For example, they are less energetic and show less interest in their surroundings than their peers. Therefore, researchers suspect that the composition of the bacterial community in the gut plays an important role in depressive symptoms.
In their new study, these scientists systematically investigated the effects of probiotics in patients with depression. All participants were patients and received either 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 they were taking during the entire study period. The researchers conducted a series of tests on the participants immediately before treatment, at the end of 31 days, and again 4 weeks later.
Further analysis showed that although depressive symptoms decreased in all participants due to general antidepressant treatment, there was a greater improvement in subjects in the probiotic group than in those in the placebo group. In addition, the composition of his intestinal flora changed, at least temporarily; in the probiotic group, analysis of stool samples revealed an increase in lactic acid bacteria at the end of treatment, an effect that was accompanied by a reduction in depressive symptoms. However, the level of these beneficial intestinal bacteria for health decreased again in the following 4 weeks. “It may be that 4 weeks of treatment is not enough and that the new composition of the intestinal flora takes longer to stabilize”, explains Anna-Chiara Schaub, one of the lead authors of the study.
Another interesting effect of taking probiotics was seen in relation to brain activity when seeing neutral or fearful faces. The researchers studied 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 4 weeks of taking 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 not yet been fully elucidated”, 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 use the best mixture to support the treatment of depression”, emphasizes
