One-way ANCOVA showed a main effect of MDD on the plasma concentrations of IL-1β (p<0.05), CXCL12 (p<0.05), CCL11 (p<0.05), and CX3CL1 (p<0.05) in the cocaine group, but no significant effects on any of these inflammatory mediators in the alcohol one. This evidence concerns the gene CXCL12 and major depressive disorder.