Relationship between chronic diseases and depression: the mediating effect of pain

Chronic diseases have a high incidence in China and may cause pain and depression. However, the association of chronic diseases with pain and the incidence of depression has not been comprehensively investigated.

The study population was obtained from the 2015 China Health and Retirement Longitudinal Study (CHARLS). The cross-sectional data from15,213 persons were included. CHARLS provides nationally representative data from21,097 individuals aged 45 years and older in approximately 150 districts and 450 villages. The main outcome was the incidence of depression. The main independent variable was chronic disease (no chronic disease, one chronic disease, and two or more chronic diseases). The mediators were the degree of pain (no pain, mild pain, and moderate to severe pain) and whether measures were taken to relieve pain (measures taken and no measures taken). We performed chi-square and binary logistic regression analyses of the associations of chronic disease with pain and the incidence of depression. The mediation model was examined using the Sobel test.

Patients with more chronic diseases had more severe pain (OR = 3.697, P < 0.001, CI = 2.919-4.681) and were more likely to develop depression (OR = 2.777, P < 0.001, CI = 2.497-3.090). The degree of pain partially mediated the interaction between chronic disease and depression in this study (t = 7.989, P < 0.001). The incidence of depression was high in people who were female, less educated, unmarried, living in rural areas, and working.

The degree of pain had a partial mediating effect on chronic disease and depression. Pain relief measures should be considered when treating patients with depression.