H2S not only attenuates homocysteine-induced apoptosis in hippocampal neurons and ERS by upregulating the expression of BDNF-TrkB in the MDD model but also improves CUMS-induced depression and inhibits hippocampus by promoting the expression of hippocampal Sirt-1 ERS (Wei et al., 2014; Liu et al., 2017). Here, BDNF is linked to major depressive disorder.