The association between gut microbiota and insomnia: A systematic review and meta-analysis

Emerging evidence suggests interactions between gut microbiota and sleep regulation, but specific associations with insomnia remain unclear. This systematic review evaluated alterations in gut microbiota in patients with insomnia compared with healthy controls. A systematic literature search was performed on eight databases from inception to June 2025. Case-control, cohort, and cross-sectional studies examining gut microbiota in adults with insomnia versus healthy controls were included. Fourteen studies encompassing 9036 participants (58.4 % female) were included. Alpha diversity was reduced in patients with insomnia in most of the included studies, among which observed species significantly decreased (SMD: 0.90, 95 % CI: 1.39, -0.40, k = 5). Beta diversity analysis revealed a consistently distinct microbial community structure between individuals with insomnia and healthy controls. Taxonomically, insomnia correlated with shifted Firmicutes-to-Bacteroidetes ratios. Meta-analyses revealed alterations in key genera, including significantly decreased Faecalibacterium and Lachnospira, and significantly increased Blautia and Eubacterium hallii. Changes in gut microbiota were also correlated with inflammatory markers and metabolic disturbances. In summary, gut microbiota dysbiosis was associated with insomnia and characterized by reduced microbial diversity and altered bacterial composition. These findings suggest potential applications for microbial biomarkers in insomnia diagnosis and subtyping, and the development of personalized microbiota-targeted interventions.