CXCL1 and major depressive disorder: In the older cohort within the High Fatigue/Low Pain class, after adjusting for BMI and KPS scores, depression scores were positively correlated with soluble GRO-α (r = 0.56, p = 0.039, n = 16), IL-1β (r = 0.55, p = 0.049, n = 15), and IL-2 (r = 0.74, p = 0.037, n = 10) and negatively correlated with EV IL-2 (r = −0.56, p = 0.046, n = 15).