While controlling for 10.13039/100030732MSD IL-6, fibrinogen levels (b = 1.619, p = .014) and its interaction terms fibrinogen × social support (b = −0.063, p = .001), and fibrinogen × social strain (b = 0.056, p < .001) significantly predicted future MDD symptoms, while CRP levels (b = −1.020, p = .158), CRP × social support (b = 0.022, p = .305), and CRP × social strain (b = 0.003, p = .853) were not significant predictors. This evidence concerns the gene IL6 and major depressive disorder.