For the outcomes of anxiety, depression, and suicide, GLP-1RAs demonstrated no overall correlation signal; dipeptidyl peptidase-4 (DPP-4) inhibitors displayed signals related to anxiety (ROR 1.14, 95%CI 1.02–1.26) and depression (ROR 1.97, 95%CI 1.74–2.23); interestingly, metformin exhibited a moderate suicide signal (ROR 4.82, 95%CI 4.31–5.39). This evidence concerns the gene DPP4 and major depressive disorder.