IL1B and major depressive disorder: Furthermore, growing evidence suggests that individuals with depression also exhibit elevated levels of circulating cytokines like IL-6 [49,60,61], IL-1β [48], TNF-α [49], IFN-α, prostaglandin E2 (PGE2), and chemokine CCL2 [49,62,63,64,65], as well as acute-phase proteins such as C-reactive protein (CRP) [66].