Objective:To explore the difference of 5-hydroxytryptamine(5-HT)between functional dyspepsia(FD)patients with or without mild-to-moderate depression and to provide theoretical basis for the treatment and assessment. Methods:Clinic patients with FD were divided into two groups based on hospital anxiety and depression scale(HADS):trial group(30 FD patients with mild-tomoderate depression)and control group of(30 FD patients without depression). The blood specimen and gastric mucosa specimen from the two groups were collected. ELISA was applied to detect 5-HT content in plasma and gastric mucosa. Results:The 5-HT content of plasma and gastric mucosa was higher in trial group than in control group

with statistically significant differences between the two groups(P=0.000). Depression score was related with the 5-HT content of plasma(r=0.921

P=0.000)and gastric mucosa(r=0.954

P=0.000). Conclusion:FD complicated with mild-to-moderate depression will incure abnormal change of neuroendocrine. 5-HT may play an important role in the course of illness and can be used as criterion to assess depression severity and antidepressant efficacy for FD patients.