TNF and major depressive disorder: Second, adults aged 40 years or younger are typically actively engaged in the labor market22, and accordingly, the combined stress of the workload and the need to cope with the clinical manifestations of depression, may insidiously aggravate the level of plasma concentrations of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-1 (IL-1) or IL-6, thus increasing the vulnerability to RA19, 23.