BACKGROUND:Clinicaly, patients with constipation often have depression and depression is often associated with symptoms of constipation, but the mechanisms remain unclear. OBJECTIVE:To observe the relation between constipation and depression by establishing animal models. METHODS:A total of 60 specific-pathogen-free rats were divided randomly into three groups: normal group, chronic stress-induced depression model group and slow transit constipation model group. Slow transit constipation model was created by giving the solution of compound diphenoxlate 8 mg/kg daily, for 120 consecutive days. On day 100, chronic stress model rats were subjected to successive unforeseen stimulus for 21 days. Rats in the normal group were regularly housed. Fecal number, dry weight of feces and body weight were recorded once a week. After successful model establishment, fecal number, dry weight of feces, time of first dark stools defecation, sucrose preference, open-field behavior score and forced swim time were detected in each group, and statisticaly analyzed. RESULTS AND CONCLUSION:Fecal number was less in the chronic stress-induced depression model group than in the normal group (P = 0.00), and time of first dark stools defecation was longer (P = 0.00). Fecal number was more in the chronic stress-induced depression model group than in the slow transit constipation model group (P = 0.00), but time of first dark stools defecation was shorter (P = 0.00). No significant difference in fluid consumption, sucrose preference, horizontal and vertical scores of open-field test, and forced swim time was detected between slow transit constipation model group and normal group (P > 0.05). However, above indexes were higher in the slow transit constipation model group than in the chronic stress-induced depression model group (P < 0.01). Results verified that constipation was observed in chronic stress-induced rat model, but depression was not observed in slow transit constipation rat model, suggesting that depression can induce constipation, but constipation does not necessarily lead to depression.