DDIT3 and major depressive disorder: For example, ERS-related proteins (such as GRP78, CHOP, and XBP1) were found to be associated with hippocampal damage and cognitive impairment in a rat model of stress, and the expression levels of ERS-related proteins (such as GRP78 and CHOP) in the hippocampus of patients with MDD were upregulated compared to those in control subjects (12, 13).