Mania in Bipolar Disorder and Microbiota

Abstract

Bipolar Disorder is characterized by recurrent episodes of mania and depression, with periods of euthymia in between. While substantial research has explored the role of gut microbiota in BD, most studies have focused on the depressive phase, leaving a significant gap in the understanding of microbiota alterations and probiotic interventions during manic episodes. Emerging evidence suggests that microbiota composition may influence neuroinflammation, neurotransmitter balance, and treatment response in BD. This systematic review synthesizes current evidence on gut microbiota alterations and the impact of probiotic interventions during manic episodes in bipolar disorder thereby addressing a critical gap in our understanding of the microbiota's role in this phase of the illness. Following PRISMA guidelines a systematic search across PubMed, Web of Science, Scopus, and CENTRAL yielded 685 studies, of which 8 met the inclusion criteria. Two studies examined microbiota composition in individuals with mania, identifying alterations in specific bacterial taxa, such as reduced Faecalibacterium and increased Streptococci levels. Three human studies explored probiotic interventions in mania, showing a reduction in symptom severity and rehospitalization rates. Additionally, three animal studies investigated microbiota alterations and probiotic treatments in mania-like behaviour, suggesting that gut microbiota influences susceptibility to mania and that probiotic administration may have therapeutic potential. These findings highlight the need for further research to clarify the causal mechanisms linking microbiota and mania, as well as to develop microbiota-targeted interventions as adjunctive treatments for BD.