Effects of probiotics on psychological issues in people with fibromyalgia: a systematic review

Background: In this systematic review, we aimed to evaluate the impacts of probiotics on psychological issues and other symptoms, such as pain and fatigue, in people with fibromyalgia. Materials and Methods: On 19 January 2025, PubMed, Scopus, and Web of Science were searched to identify relevant records. We included studies that evaluated the effects of probiotics, either alone or in combination with other treatments, in individuals diagnosed with fibromyalgia, compared to the placebo or any other form of treatment. The quality of the included studies was assessed using the JBI critical appraisal tools for randomized controlled trials and quasi-experimental studies. We used a qualitative approach for the synthesis in this study. Results: From a total of 186 articles retrieved in our search, five reports from four studies were included in this review. In total, 209 people with fibromyalgia were included in these studies, with 103 (49.3%) being in the experimental (probiotic) group. All studies fulfilled the majority of the JBI critical appraisal tool criteria. Although some studies reported reductions in anxiety and depression among individuals with fibromyalgia who used probiotics, the findings were not consistent across all studies. Only one study assessed adverse events associated with probiotics compared to placebo, finding no significant differences between the groups in the incidence of at least one adverse event ( P > 0.05). Conclusions: Overall, we cannot make a definitive recommendation for or against the use of probiotics in the treatment of individuals with fibromyalgia, and future studies are needed in this regard.