Pro-inflammatory cytokine associated with somatic and pain symptoms in depression

Abstract

Background: More than two-thirds of depressed patients complain of somatic and pain symptoms, which are frequently regarded as a psychological reaction. Although there is a growing body of evidence showing that depression is related to immune abnormalities, few studies have investigated the association between inflammatory cytokines and somatic/pain symptoms.

Method: Patients with depressive disorder but without any medical disorders, and age/gender/body mass index (BMI)-matched healthy subjects were enrolled. All the subjects completed the self-rating scales of the Beck Depression Inventory-II and the Depression and Somatic Symptoms Scale, which was comprised of depressive, somatic, and pain subscales. Pro-inflammatory cytokines, including C-reactive protein (CRP), interleukin-2 receptor (sIL-2R), soluble interleukin 6 receptor (sIL-6R), soluble TNF-receptors (sTNF-R), soluble P-selectin (sP-selectin), monocyte chemotactic protein-1 (MCP-1), and adiponectin, were assessed by enzyme-linked immunosorbent assays.

Results: In all, 109 patients with depressive disorder and 126 normal controls were enrolled. The patients with depressive disorder had significantly more severe depression, somatic and pain symptoms (all p<0.001), and higher levels of sIL-2R (p<0.0001), sTNF-R (p<0.001), and sP-selectin (p=0.005) than the normal control group. Using multivariate regression analysis with controlling of age, gender, BMI, and other pro-inflammatory cytokines, sIL-2R was the most significant predictor for depressive symptoms (p<0.0001); with further controlling of severity of depressive symptom, sP-selectin was the only predictor for somatic (p=0.002) and pain (p=0.059) symptoms.

Conclusion: The elevated sP-selectin associated with somatic symptoms in depression, may indicate early micro-vascular changes occur subtly, and provide neurobiological evidence for somatic and pain symptom in depression.

Keywords: Depression; Pro-inflammatory cytokines; Somatic and pain symptoms.