Objective To explore the expression changes of SIRT1 and related inflammatory regula-tors in peripheral blood of patients with major depressive disorder and analyze the correlation between SIRT1, depression and inflammatory regulators. Methods Forty patients with major depressive disorder and forty healthy controls were selected. Hamilton Depression Scale (HAMD-17) was used to assess the degree of de- pression in patients with depressive disorder. Quantitative Real-time PCR( RT-PCR) was used to detect the relative expression levels of SIRT1,Elf-1,NF-κB,IL-1β,GM-CSF mRNA,and enzyme linked immunosorbent assay(ELISA) was used to detect the expression levels of SIRT1,Elf-1,NF-κB,IL-1β,GM-CSF proteins. The correlation between the severity of depression disorder and SIRT1 and the correlation between SIRT1 and Elf-1 and NF-κB were analyzed. Results (1)Compared with the control group,SIRT1 mRNA expression significantly decreased in the case group (P<0. 01),while Elf-1,NF-κB,IL-1β,GM-CSF mRNA expression significantly increased in the case group (P<0. 01). ( 2) The expression of plasma SIRT1 protein((8. 23± 1. 78)ng/ml) in the case group was lower than that in the control group (P<0. 01). The expressions of plas-ma Elf-1 protein((1 921. 67±271. 07)pg/ml),NF-κB protein((2 057. 29±260. 44)pg/ml),IL-1β protein ((186. 60±31. 00) pg/ml) and GM-CSF protein((183. 69±28. 87) pg/ml) were higher than those in the control group((1 512. 92±284. 54)pg/ml,(1537. 18±313. 82) pg/ml,(144. 79±31. 48) pg/ml,(162. 82± 27. 90) pg/ml,respectively,all P<0. 01). (3) SIRT1 mRNA expression level was negatively correlated with the severity of major depressive disorder (r=-0. 51, P<0. 01) and was negatively correlated with the mRNA expression levels of Elf-1 and NF-κB (r=-0. 66,P<0. 01,r=-0. 64,P<0. 01). Conclusion The expres-sion level of SIRT1 in peripheral blood of patients with major depressive disorder is correlated with the sever-ity of depression. This may be related to the decrease of SIRT1 expression in peripheral blood leukocytes of patients with major depressive disorder,which activates the pathway of NF-κB and Elf-1 and increase expres-sion of GM-CSF and IL-1β.