Psychobiotics in the treatment of depression: a new look at mental health – a systematic search review

Abstract

Major Depressive Disorder (MDD) is a multifactorial psychic disorder, conventionally treated with antidepressant medications. The symptoms caused by the depressive symptomatology itself and the side effects caused by the medications are some of the factors that negatively interfere in the adherence to pharmacological treatments. Currently, after probiotics have shown psychotropic effects, the scientific field has intensified efforts to understand whether probiotic supplementation serves as a treatment for psychiatric disorders. Therefore, the present study formulated the following question: can psychobiotics (probiotics) be denoted as a treatment for Major Depressive Disorder? Objective: to answer the guiding question through a review of studies that supplemented psychobiotics with the intention of treating Major Depressive Disorder. Methodology: for this review, a systematic search was designed, where, during the month of September 2021, the searches took place in the databases; Pubmed, Google Scholar, and Scielo, using the descriptors “probiotics AND depression AND dysbiosis” in English and Portuguese, and filters for the selection of studies published between 2005 and 2021. After selecting the materials, the duplicates were managed in EndNote, and the methodological quality of randomized trials was assessed using the Risk of Bias-2 (ROB 2) tool. Results: there was a preference for 10 studies; preclinical (n=4), randomized (n=5) and open pilot (n=1), which met the inclusion criteria, and showed significant results on depression scores on psychiatric scales; demonstrating the decrease in anhedonia, cognitive reactivity, and insomnia in patients diagnosed with Major Depressive Disorder, in addition, significant changes were observed on factors that may be associated with the pathogenesis of depression, such as dysbiosis, and the inflammatory state in the face of the decrease of inflammatory biomarkers. Final considerations: according to the data review, the following answer was obtained for the guiding question: psychobiotics can be denoted as a treatment for Major Depressive Disorder. However, due to the need for a better understanding of the gut-brain axis and the mechanisms of action of psychobiotics, supplementation is recommended as an adjunctive therapy to antidepressant drugs. Therefore, studies with larger samples and longer intervention periods should be performed.