In the subgroup analysis focusing on drug classes for diabetes treatment, DPP-4 inhibitors showed signals associated with depression (ROR:1.42, 95% CI: 1.28–1.57), metformin showed signals associated with suicide (ROR:2.04, 95% CI:1.83–2.27), while other antidiabetic drugs, including GLP-1 RAs, did not show relevant signal risks (Figure 6A). This evidence concerns the gene DPP4 and major depressive disorder.