Suarez et al., (2004) found that both the severity of depressive symptoms, measured by the 21-item Beck Depression Inventory (BDI), and hostility, assessed using the 50-item Cook–Medley Hostility (Ho) scale, independently and synergistically increase IL-8 expression in healthy premenopausal women [343]. This evidence concerns the gene CXCL8 and major depressive disorder.