A meta-analysis found that higher levels of IL-6 and CRP are associated with an increased risk of psychological and immunological changes, including all-cause dementia and depression; IL-1 β has been identified as an important risk factor for depressive symptoms and plays a key role in neurodegenerative changes by involving in the pathogenesis of the production and deposition of amyloid β-protein in the brain of Alzheimer’s disease (128). Here, IL6 is linked to major depressive disorder.