TNF and major depressive disorder: In a more recent study by the same research group [28], a significant negative correlation between serum 25(OH)D levels and neutrophile-to-lymphocyte ratio (NLR), white blood cell (WBC) count, as well as inflammation composite score (calculated by summarizing the z-scores of tumor necrosis factor alpha (TNF-α) and IL-6) was found in subjects with major depressive disorder (MDD) and suicidal ideation (n = 17), but neither in healthy controls (n = 54) nor in patients with MDD without suicidal ideation (n = 31).