Abstract: Objective To investigate the mediating effect of loneliness on the relationship between social constraints and depression in breast cancer patients and inform the reduction of the incidence of depression in breast cancer patients. Methods Data were collected from 257 breast cancer patients at a hospital in Jiangsu province using three scales: the Patient Health Depression Questionnaire, Social Constraints Scale, and Cancer Loneliness Scale. General information was then analyzed. Results Depression, social constraints and loneliness scores of breast cancer patients were 6.63±3.15, 30.71±7.73 and 21.24±5.21 respectively. Depression was positively connected to social constraints and loneliness, and social constraints was positively connected to loneliness(r=0.498,r=0.396,r=0.639, all P<0.01). The loneliness of breast cancer patients has a partial mediating effect between social constraints and depression, with the mediating effect making up 27.15% of the total effect. Conclusion Medical workers should take measures to reduce the social constraints of breast cancer patients and reduce the loneliness so as to reduce the occurrence of depression.

Key words: breast cancer, depression, social constraints, loneliness, mediating effect