Positive correlations were found between the HAMD scores and the CD4+/CD8+ T-cell ratio (r=0.571, p<0.001) and SII (r=0.464, p<0.001), PSQI global scores and SII (r=0.219, p=0.045), SII and the percentage of CD3+CD8+ T cells (r=0.310, p=0.004) in patients with CHD with MDD. Here, CD4 is linked to major depressive disorder.