Research reportEstablishment 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.

BackgroundDepression 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.MethodsRats 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.ResultsThe sucrose preference was significantly reduced in the depressed rats (p < 0.01) and contagion depression rats (p < 0.01). Climbing time during forced swim test was reduced in the depression and contagion depression groups (p < 0.001), whereas immobility time was significantly prolonged in only the depression group (p < 0.001). Rats in both the depression (p < 0.05) and depression contagion group (p < 0.005) had decreased total travel distance and decreased mean velocity in the open field test, whereas the time spent in the central part was significantly shorter in only the depression group (p < 0.001).ConclusionsIn this study, for the first time we demonstrated depression contagion in an animal model. A reliable animal model may help better understand the underlying mechanisms of contagion depression, and may allow for future investigations of the studying therapeutic modalities.