The circadian rhythm is an internal timing system formed by the body's adaptation to the Earth's rotation, which helps maintain homeostasis by regulating physiological, metabolic, and behavioral activities. The gut microbiota (GM), the largest microbial ecosystem in the human body, exhibits a bidirectional regulatory relationship with the host circadian clock. Emerging evidence indicates that circadian rhythm disruption (CRD) is linked to disturbances in the diurnal oscillations and compositional balance of the GM, accompanied by reduced short-chain fatty acid levels, increased lipopolysaccharide leakage, and altered tryptophan metabolism. These microbial abnormalities may be involved in anxiety-like behaviors through three major pathways: neuroendocrine (hyperactivation of the HPA axis), immune (microglia-mediated neuroinflammation), and neurotransmitter (imbalance of the serotonergic and dopaminergic systems). Conversely, microbial metabolites such as butyrate and secondary bile acids may reciprocally regulate peripheral clock gene expression, forming a complex "circadian rhythm-GM-anxiety" interaction network. This review summarizes the molecular basis of circadian-GM interactions, potential GM-mediated mechanisms linking CRD with anxiety, and emerging intervention strategies including chrononutrition (time-restricted feeding, sequential nutrient intake), microbiota-targeted therapies (probiotics/prebiotics, fecal microbiota transplantation), and light therapy and melatonin supplementation. Future directions should focus on cell-specific mechanisms using single-cell and spatial transcriptomics, developing personalized interventions that integrate chronotype and microbiome profiling, and conducting large-scale randomized controlled trials to facilitate clinical translation. This review provides a framework for understanding the integrative role of circadian biology and gut microbiota in anxiety and may help develop precision intervention paradigms.
