As a member of FGF family, FGF22 has been found to be significantly associated with the occurrence of epilepsy, cancer, depression and other diseases as well as embryonic brain development (Jarosz et al., 2012; Singh et al., 2012; Lee and Umemori, 2013; Miyake and Itoh, 2013). Here, FGF22 is linked to major depressive disorder.