TNF and major depressive disorder: The results of the bivariate Spearman correlation analysis showed that age was positively associated with IL-5 (r = 0.306, P = 0.009), TNF-α (r = 0.350, P = 0.003), IL-6 (r = 0.263, P = 0.025), sleep disturbance (r = 0.257, P = 0.029), and depression (r = 0.340, P = 0.004), but negatively associated with irritability (r = −0.321, P = 0.006).