The gut-brain axis and depressive symptoms: a systematic review of randomized clinical trials with probiotics

ABSTRACT Objective: Currently, the gut-brain axis has been highlighted as an important aspect for understanding behavior and mental illnesses. The present study aimed to analyze the effects of probiotic consumption on depressive symptoms and major depression. Methods: A review of randomized, double or triple blind and placebo-controlled trials, published between 2010 and 2020, was performed in PubMed, ScienceDirect and Google Scholar. Results: Eight articles were selected to compose the sample. Findings between studies are controversial, and indicate that a causal relation between probiotic consumption and relieve of depressive symptoms is not yet established. Conclusion: More randomized, double or triple blind, placebo-controlled trials are necessary to consistently verify the causal relation between probiotic consumption and relieve of depressive symptoms.