For example, eCB is downregulated in numerous models of fear-, depression-, anxiety-, and trauma-related disorders, and inhibiting the synthesis of eCB by overexpressing FAAH significantly increases sensitivity to negative emotions, contextual fear memory, loss of interest, etc. (Korem and Akirav, 2014; Segev et al., 2014; McEwen et al., 2015). This evidence concerns the gene FAAH and major depressive disorder.