A recently published scientific report from Basel, Switzerland, has demonstrated that probiotics can supplement antidepressant treatment. The report titled “Clinical, gut microbial and neural effects of a probiotic add-on therapy in depressed patients: a randomized controlled trial” was published in ‘Translational Psychiatry.’
Major depressive disorder (MDD) is one of the most common psychiatric disorders. However, the initial antidepressant therapy is ineffective for two-thirds of depressive individuals, and up to 30% of patients who are resistant to treatment experience symptoms even after obtaining optimal care. Therefore, there is an urgent need for new and more effective therapeutic approaches.
Compelling preclinical evidence (research done on animals) showed how gut microbiota influences brain functioning and depressive behavior, making it a viable new target for the treatment of depression. Randomized controlled clinical trials (RCT) also revealed improvement in patients with MDD’s self-reported depression symptoms following an eight-week probiotic treatment.
Moreover, according to preliminary studies, antidepressants increased gut microbiota diversity, and particular bacteria, including Ruminococcus flavefaciens, eliminated the antidepressant impact of duloxetine on depressive-like behavior in rats.
How Was This Study Conducted?
Probiotic add-on therapy for four weeks was tested in this double-blind RCT on depressive patients in this study. Participants met the eligibility requirements, including using the Hamilton Rating Scale for Depression, being over 18, and receiving regular therapy for depression. Patients who were immunosuppressed, had dietary limitations, or had illnesses including acute infectious infections were not included. Additionally, concomitant psychiatric conditions like addiction, bipolar disorder, and schizophrenia were disqualifying factors, as were being pregnant or nursing.
Out of 60 participants enrolled in this study, 47 completed the intervention (Probiotics=21, Placebo=26), suggesting a dropout rate of 30% in the probiotics group and 13% in the placebo group. All individuals received antidepressants and either a probiotic (21 subjects) or a placebo (26 subjects) for 31 days.
Throughout the trial, neither the participants nor the research team were aware of the medication intake of individual subjects. The researchers put the participants through a battery of tests before therapy, at the end of the 31 days, and once more four weeks later.
What Are the Key Findings of the Study?
The subsequent analysis revealed that although all participants’ depressed symptoms improved as a result of receiving general antidepressant therapy, there was a greater improvement in the patients of the probiotic group than in the placebo group.
In the probiotic group, a stool sample analysis at the end of treatment revealed an increase in lactic acid bacteria, which was associated with a decline in depression symptoms.
Another intriguing effect of taking probiotics was the normalization of the altered brain activity in depression patients of the probiotic group after four weeks, but not in the placebo group.
What Was the Relationship Between Probiotic Use and Gut Microbes?
According to these findings, probiotics may be able to slow down the deterioration of the gut bacterial flora, which happens in depression during the intervention period. Further evidence that probiotics support the maintenance of a healthy bacterial community comes from the fact that the healthy Prevotella enterotype decreased in the placebo group but not in the probiotic group.
Administration of probiotics increased the variety of Lactobacillus strains. The probiotics’ antidepressant effects might be linked to the rise in the population of the species in the gut. This is in line with previous research, which demonstrated that an increase in the Lactobacillus genus population lowered corticosterone levels brought on by stress, symptoms of anxiety, and sadness.
Schaub, AC., Schneider, E., Vazquez-Castellanos, J.F. et al. Clinical, gut microbial and neural effects of a probiotic add-on therapy in depressed patients: a randomized controlled trial. Transl Psychiatry 12, 227 (2022). https://doi.org/10.1038/s41398-022-01977-z