IL6 and major depressive disorder: Compared with controls, IL-1β (pooled standardized mean difference [SMD]: 0.642; 95% confidence interval [CI]: 0.078–1.206; significant heterogeneity: I2 = 86.28%) and IL-6 (pooled SMD: 0.377; 95% CI: 0.156–0.598; significant heterogeneity: I2 = 88.75%) were significantly elevated in depression.