Depressive Symptoms Moderate the Influence of Hostility on Serum Interleukin-6 and C-Reactive Protein

Address correspondence and reprint requests to: Jesse C. Stewart, PhD, E-mail: jstew{at}iupui.edu.

	Abstract

Objective: Recent evidence suggests that depressive symptoms and hostility may act together, as interacting factors, to have an effect on the circulating levels of inflammatory markers relevant to coronary artery disease. Further research, however, is needed to clarify the nature of this interaction and to determine whether previous findings extend to older adults. In this report we examined the cross-sectional associations of depressive symptoms, hostility, and their interaction with circulating levels of two such inflammatory markers—interleukin-6 (IL-6) and C-reactive protein (CRP). Methods: A total of 316 healthy, older adults underwent a blood draw for the assessment of serum IL-6 and CRP and completed the Beck Depression Inventory-II and the Cook-Medley Hostility Scale. Regression analyses were performed to examine depressive symptoms, hostility, and their interaction as predictors of serum IL-6 and CRP. Results: After adjustment for demographic factors, cardiovascular risk factors, and health behaviors, we detected depressive symptoms x hostility interactions for serum IL-6 (R² = .027, p < .01) and CRP (R² = .015, p < .05). Simple slope analyses revealed that hostility was positively related to serum IL-6 only among individuals with higher depressive symptoms. The pattern of results was similar for serum CRP, although none of the simple slopes was significant. Conclusions: Our findings suggest that depressive symptoms may moderate the hostility-inflammation relationship such that hostility may augment inflammatory processes relevant to coronary artery disease only in the presence of depressive symptoms. Our results also extend previous findings from younger adults to older adults from the general community.

Key Words: depression, hostility, inflammation, interleukin-6, C-reactive protein, coronary artery disease