To explore the pathogenesis of anxiety and depression-anxiety（hereinafter referred to as “comorbidity”）in the rat model and the regulatory effects of Jiawei Wendan Decoction（加味温胆汤）based on the changes in the diversity and composition of the gut microbiota.

Fifty-six SPF male SD rats（180～200 g）were randomly divided into the normal control group, model groups（anxiety model group and comorbidity model group）, traditional Chinese medicine（TCM）groups（anxiety TCM group and comorbidity TCM group）, and Western medicine groups（anxiety Western medicine group and comorbidity Western medicine group）. The anxiety and comorbidity models were established using predator exposure stress and chronic restraint stress, respectively. The normal control group and model groups were given the normal saline gavage, while the TCM groups were given Jiawei Wendan Decoction（12 g/kg）by gavage. The anxiety Western medicine group and comorbidity Western medicine group were given paroxetine and probiotics（1.8 mg/kg）by gavage, respectively. After 35 days, the behavioral testing and sampling were conducted. The diversity and compositional changes of the gut microbiota in each group were analyzed using high-throughput 16S rRNA sequencing.

The behavioral data showed that in the anxiety model group, the number of horizontal movements, vertical movements and total distance was significantly decreased compared to those in the normal control group（P < 0.05）. Jiawei Wendan Decoction improved the number of vertical and horizontal movements（P < 0.05）but had no significant effect on total distance. The anti-anxiety drug paroxetine improved the number of vertical movements but showed no significant effects on other parameters（P < 0.05）. In the comorbid model group, the number of horizontal movements, vertical movements and total distance were significantly increased compared to those in the normal control group（P < 0.05）. Jiawei Wendan Decoction significantly affected the total distance（P < 0.05）, and probiotics improved the number of vertical movements and total distance（P < 0.05）but had no significant effect on horizontal movements. Compared to the normal control group, the anxiety model group showed a decrease in ACE, Chao1, PD_whole_tree and Shannon indices, whereas the comorbid model group showed slight increases in these indices. The relative abundances of Firmicutes and Allobaculum were higher in the TCM group for anxiety. Moreover, the relative content of Lactobacillus intestinalis in the samples showed an increasing trend compared with the anxiety model group, and the reduction of Lactobacillus johnsonii was improved. Compared with the comorbidity model group, the proportions of Allobaculum, Lactobacillus, Lactobacillaceae and Lactobacillales were particularly significant in the comorbidity TCM group. Additionally, the relative abundance of the Lactobacillus johnsonii population increased substantially, and this enhancement was superior to that in the comorbidity western medicine group and the model group.

Jiawei Wendan Decoction showed advantages in regulating the intestinal microbiota of anxiety and comorbidity model rats. It not only improved the diversity and structure of intestinal microbiota, but also increased the contents of probiotics, enhanced the expressions of genes related to environmental information processing, and effectively regulated the microbial communities related to aging and neurodegenerative diseases, demonstrating the potential therapeutic advantages.