Association of IL-6, Hypothalamus-Pituitary-Adrenal Axis Function, and Depression in Patients With Cancer

Background: Evidence suggests that cytokines (IL-6) and alteration of the hypothalamic-pituitary-adrenal (HPA) axis play a crucial role in the etiology of depression. Patients with cancer show elevated prevalence rates for depression. The objective of this cross-sectional study was to investigate the associations between these abnormalities and depression. Methods: Plasma concentrations of IL-6 and cortisol were measured in cancer patients with (N = 31) and without depression (N = 83). The relative diurnal variation of cortisol (cortisol VAR), expressed in percentage, was calculated. Results: There was a significant difference in median plasma concentration of IL-6 between the patients with depression and those without (18.7 vs 2.7 pg/mL; P < .001). Relative cortisol VAR was decreased in depressed patients as compared with patients without depression (11.72% vs 60.6%, P = .037). A positive correlation between the depressive symptoms and IL-6 concentration was found (r = 0.469, P < .001). Negative correlations were found between cortisol VAR versus depressive symptoms and cortisol VAR versus IL-6 (r = -0.6, P < .001 and r = -0.52, P < .001, respectively). IL-6 (odds ratio [OR] = 1.1; 95% confidence interval [CI] = 1.0-1.2; P = .006) and cortisol VAR (OR = 1.3; 95% CI = 1.0-1.4; P = .02) are independently associated with depression. Conclusions: Depression in cancer is associated with increased plasma IL-6 concentrations and dysfunction of the HPA axis.