TNF and major depressive disorder: Median concentrations of another pro-inflammatory cytokine TNF-α were highest in the Depression (1.47 log pg/mL) group, followed by the Control (1.12 log pg/mL) and Abuse (0.43 log pg/mL) groups with mostly undetectable values for the Abuse+Depression group (p<0.01) (Fig 2D, Table 2B).