Genome-wide association studies and epigenetic analysis revealed that genetic variants associated with depression were significantly enriched in epigenetic active sites of activated CD4+T lymphocytes, which may affect immune cell function, promote the increase of peripheral blood inflammatory markers (CRP, IL-1β, TNF-α, IL-6, IL-17) and increase leukocyte count, suggesting that the immune system may participate in the pathogenesis of MDD through inflammatory response (Lynall et al., 2022). Here, IL6 is linked to major depressive disorder.