What is already known
Research done in animal models has shown that gut microbes can influence brain function and depressive symptoms, and recent studies have reported alterations in gut microbiota composition in people with depression. Probiotic treatments may be a tool for improving mood in people suffering from several conditions, but how such treatments would play out in depressed people remains unclear.
What this research adds
For 31 days, researchers gave either a probiotic supplement or a placebo to people with depression, in addition to antidepressants. Antidepressant treatment led to a decrease in depressive symptoms in all participants, but people who received the probiotic experienced a greater improvement than those who received a placebo. The probiotic supplement resulted in temporary changes in the composition of the microbiota, with an increase in Lactobacillus species at the end of treatment. The probiotic also changed the activity of brain areas involved in the processing of emotions.
Conclusions
The findings suggest that probiotic supplements could improve depressive symptoms as well as gut microbiota composition and brain activity. Probiotic treatment may thus be used in combination with antidepressant medication to treat clinical depression.
Major depressive disorder, also known as clinical depression, is a mental condition characterized by at least two weeks of pervasive low mood. Two-thirds of depressed people do not respond adequately to antidepressant medication and up to 30% of those continue to experience symptoms even when receiving optimized treatments. Now, a small clinical trial shows that a probiotic supplement may help to improve depressive symptoms when given in addition to antidepressants.
The findings, published in Translational Psychiatry, suggest that probiotic treatment could be used in combination with antidepressant medication to treat clinical depression. “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 lead study author Anna-Chiara Schaub at the University of Basel.
Research done in animal models has shown that gut microbes can influence brain function and depressive symptoms, and recent studies have reported alterations in gut microbiota composition in people with depression. Probiotic supplements may be a tool for improving mood in people suffering from several conditions, but how such treatments would play out in depressed people remains unclear.
Schaub and her colleagues assessed the effect of a probiotic supplement, given in addition to antidepressant medication, on depressive symptoms in people with clinical depression.
Small trial
All the study participants were inpatients at the University Psychiatric Clinics in Basel. For 31 days, in addition to antidepressant medication, 21 participants received a probiotic containing eight different bacterial strains, including Streptococcus thermophilus, Bifidobacterium breve and Bifidobacterium infantis. A second group of 26 participants received a placebo supplement in conjunction with antidepressants.
Researchers collected clinical measures, brain imaging scans, stool samples and other data before the intervention, directly after it and again four weeks after the intervention.
Antidepressant treatment led to a decrease in depressive symptoms in all participants, but people who received the probiotic experienced a greater improvement than those who received a placebo, the researchers found.
Tackling depression
At baseline, the microbiotas of study participants were dominated by Feacalibacterium, Roseburia, Bacteroides and Blautia. After four weeks of treatment, people who received the probiotic supplement had increased abundances of Lactobacillus, which was associated with reduced depressive symptoms. None of these effects were observed in people who received a placebo.
However, the levels of Lactobacillus bacteria decreased over the weeks following the treatment, the team found. “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” Schaub says.
The probiotic also changed the activity of certain brain regions involved in the processing of emotions, the researchers found. In people with depression, such activity is known to be different from that observed in people with good mental health. After four weeks of probiotic treatment, brain activity normalized in people who received the probiotic but not in those who got the placebo.
“The present findings highlight the role of the microbiota-gut-brain axis in [major depressive disorder] and emphasizes the potential of microbiota-related treatment approaches as accessible, pragmatic, and non-stigmatizing therapies to improve the effectiveness of current treatments in depression” the researchers say.
