Establishment of an animal model of depression contagion

•Healthy rats developed depressive-like behaviors when housed for long periods of time with depressive rats.•The method used in this study can be used as an animal model of contagion depression.•According to the behavioral tests, naive rats developed contagion depression after 5 weeks of cohabitation in the same cage with the depressed rats. Depression is a common and important cause of morbidity, and results in a significant economic burden. Recent human studies have demonstrated that that depression is contagious, and depression in family and friends might cumulatively increase the likelihood that a person will exhibit depressive behaviors. The mechanisms underlying contagion depression are poorly understood, and there are currently no animal models for this condition. Rats were divided into 3 groups: depression group, contagion group, and control group. After induction of depression by 5 weeks of chronic unpredictable stress, rats from the contagion group were housed with the depressed rats (1 naïve rat with 2 depressed rats) for 5 weeks. Rats were then subjected to sucrose preference, open field, and forced swim tests. The sucrose preference was significantly reduced in the depressed rats (p