Several cohort studies have found that the increase of serum levels of proinflammatory factors (such as IL-6, IL-17, TNF-α, and IL-1β) in the acute phase after stroke is independent predictors of depression when using logistics regression analysis (Kim et al., 2017; Hu J. et al., 2019), and reducing the expression of IL-6, TNF-α, and IL-1β in the cortex and hippocampus alleviated depression-like behavior in rats with PSD (Yan et al., 2019). Here, IL6 is linked to major depressive disorder.