IL6 and major depressive disorder: Additionally, meta-analytic data reviewed by Irwin et al. (2016) [13] involving over 50,000 individuals demonstrated that both sleep disturbance and altered sleep duration (frequent features of depression and anxiety) were significantly associated with elevated CRP and IL-6 (effect size for IL-6: 0.20; CRP: 0.12), supporting the strong inflammatory component of neurocognitive and mood dysregulation [13].