The intestinal flora also plays an important role in our mental health, as a study shows: By influencing the bacterial community in the intestine with probiotics, the success of antidepressant therapy can be significantly improved. The mood of the patients is brightened by the increased colonization of the intestine with certain bacteria and a typical side effect of depression is alleviated, the scientists report. According to them, however, further research should now explore the potential of using probiotics in therapy in even more detail.
Important tiny creatures live inside of us: The health significance of the bacteria in our digestive system has increasingly come into the focus of science in recent years. It was shown that the composition of the intestinal flora is not only linked to the immune system and purely physical effects, but also to neurodegenerative diseases and psychological problems. Certain features of the human microbiome have been linked to the development of depression and anxiety, for example. Apparently certain intestinal bacteria can influence the nervous system via their metabolic products. This so-called gut-brain axis has now developed into an important field of research.
Probiotic add-on therapy
The scientists led by Anna-Chiara Schaub from the University of Basel are specifically addressing the question of the extent to which the use of probiotics as part of drug treatment for depression can have a beneficial effect. As they explain, there is a need for ways to improve existing therapies and develop new ones. Although antidepressants can often lighten the dark mood of those affected, the effect leaves a lot to be desired in many cases and the decisive kick to stabilize the quality of life again in the long term is missing.
A total of 47 volunteers who had been admitted to psychiatric hospitals for inpatient treatment for their depression took part in the study. Before the start of therapy, the researchers recorded the depressive state of the patients using standard tests, and their brain reactions to certain stimuli were also recorded using functional magnetic resonance imaging (fMRI). The therapy then began, in which half of the subjects took a probiotic in addition to standard antidepressants for 31 days. It was a commercially available preparation containing eight different strains of bacteria from the group of lactic acid bacteria, which are believed to have beneficial effects. The control group, on the other hand, unknowingly received a dummy preparation (placebo) without bacteria content. To accompany the experiment, the researchers subjected all study participants to a series of tests.
mood-enhancing effect
The results showed that the antidepressants fundamentally reduced the depressive symptoms in all subjects. But in the probiotics group, the mood of the study participants improved significantly more than in the placebo group, the scientists found. The effect was also accompanied by a change in the intestinal flora: in the probiotics group, examinations of stool samples confirmed the increase in lactic acid bacteria in the composition of the intestinal microbial community. After stopping the probiotics, however, the proportion of these microbes decreased significantly over the next four weeks, the researchers found. “Perhaps four weeks of treatment is not long enough and the new composition of the intestinal flora only stabilizes after a longer period of time,” says Schaub.
Another effect of taking probiotics was affecting brain activity, the team reports. It is known that certain brain regions responsible for emotional processing react differently in patients with depression than in mentally healthy people. This is also reflected in certain patterns when looking at neutral and fearful faces, which the researchers recorded using fMRI. As the study showed, the corresponding brain activities normalized in the subjects in the probiotics group. However, the researchers were unable to determine this effect in the placebo group.
The results now illustrate the potential of using probiotics in therapy for mental health problems, say the researchers. According to them, they are not suitable as sole therapy in the clinical treatment of depression, but the additional effect could be important. However, there is a need for further research, emphasizes Schaub: “The microbiome-gut-brain axis has been a topic of research for several years, but the exact mechanisms are still only partially clear. With additional knowledge about the specific effects of certain bacteria, it would be possible to optimize the selection of bacteria and use the best mixture to support therapy for depression,” says the researcher.
Source: University of Basel, specialist article: Translational Psychiatry, doi: 10.1038/s41398-022-01977-z