In a small cross-sectional study comparing patients with depression and healthy controls, positive correlations were identified between depression severity (as measured on the clinician-administered HAM-D17) and inflammatory markers Toll-Like Receptor 4 (TLR4) and Triggering Receptor Expressed on Myeloid Cells 1 (TREM-1), depression severity and total CTQ scores, and total CTQ scores and IL-1 β, Cyclooxygenase-2 (Cox-2), and TLR4. This evidence concerns the gene TLR4 and major depressive disorder.