Objective: Previous research has revealed a relationship of depressive symptoms and hopelessness with cardiovascular diseases (CVDs) which are associated with elevated levels of interleukin-6 (IL-6). The objective of this study was to explore whether depressive symptoms and hopelessness are independent predictors of IL-6 levels.
Method: Hopelessness, depressive symptoms, and IL-6 were measured in 45 Swedish adults (26 women and 19 men; age range: 31-65 years). Two separated linear regressions were conducted with hopelessness and depressive symptoms serving as individual predictors of IL-6. Another regression analysis examined whether the two predictors predict IL-6 when controlling for each other. The regression coefficients of the models with one predictor and with both predictors were compared.
Results: As predicted, after adjusting for age, BMI, illness, smoking, and gender, more depressive symptoms and more hopelessness predicted higher IL-6 levels in independent regressions. When controlling for each other, hopelessness, but not depressive symptoms, predicted IL-6 levels. Finally, when controlling for hopelessness, the regression between depressive symptoms and IL-6 level was significantly reduced; however, there was no significant change in the regression between hopelessness and IL-6 level when controlling for depressive symptoms.
Conclusions: Thus, these results suggest that depressive symptoms and hopelessness are not independent predictors of IL-6 levels. Future research should explore the interplay of hopelessness and depressive symptoms on other risk factors of CVDs.