Regarding MDD, between 32.7% and 57.3% of the executive functioning variance at TY was explained by leukocyte [white blood cell-neutrophils (WBC-N), -absolute neutrophils (WBC-AN), and -monocytes (WBC-M)] and pro-inflammatory activity (IL-6, IL-10, TNF-α, and CRP) together with oxidative stress biomarkers (ROS and SOD). This evidence concerns the gene IL6 and major depressive disorder.