Efficacy of Probiotics, Prebiotics, and Symbiotics for the Treatment of Depression: A meta-review

Background. Recent research has highlighted the importance of nurturing and strengthening the intestinal microbiota due to its relationship with mental health, which has implications for the prevention and management of mental diseases such as depressive disorders. One opportunity to address this is supplementation with live microorganisms called probiotics or substances that promote their development called prebiotics, or both (symbiotics). Objective. This study aims to explore the existing literature on the efficacy of probiotics, prebiotics, and symbiotics for the treatment of depression symptoms and depression. Method. A meta-review of systematic reviews was conducted across various databases (Medline/PubMed, Web of Science, Scopus, Cinahl, and PsycInfo). Formulation of a research question and a comprehensive search strategy employing keywords and Boolean operators guided the identification of systematic reviews reporting quantitative synthesis, particularly meta-analysis of randomized controlled trials (RCT). Systematic reviews meeting these criteria were selected, and relevant findings were systematically extracted. Results. Thirteen systematic reviews with meta-analyses of RCT were selected. The evidence points towards the efficacy of prebiotics, probiotics, and symbiotics in depression treatment, albeit with a weak effect. Conditions optimizing the antidepressant efficacy of these supplements were identified, including their use as adjunctive therapy to pharmacological treatment, concurrent use of probiotics and prebiotics (or symbiotics), and the use of multi-strain formulations. Discussion and conclusion. Prebiotics, probiotics, and symbiotics are considered to demonstrate substantive evidence of their efficacy in the treatment of depression. Nevertheless, various research opportunities within this field have been identified.