Since hippocampus is considered to be one of the most important areas involved in stress and depression, and our previous study has demonstrated that TNF‐α is a common risk factor in depressive disorders induced by both stress and inflammation (Guan, Lin, & Tang, 2015), expression of hippocampal TLR4 as well as TNF‐α was examined in the current study. Here, TLR4 is linked to major depressive disorder.