Our findings signaled that the levels of glutamic acid and phosphatidylcholine (32:0) were consistently elevated in the blood of patients with depression, while those of tryptophan, kynurenic acid, kynurenine, acetylcarnitine, serotonin, creatinine, inosine, phenylalanine, and valine were lower. In urine samples, the concentrations of isobutyric acid, alanine, and nicotinic acid were increased, whereas those of N-methylnicotinamide and tyrosine were decreased. A thorough examination of 23 proteomic studies unveiled that only one protein, ceruloplasmin, was consistently altered in the blood of patients with depression. Besides, a convergence comparison was also performed to prioritize circulating metabolites. The top-ranked metabolite was tryptophan, followed by kynurenic acid, acetylcarnitine, creatinine, serotonin, and valine