SSTR4 and major depressive disorder: The somatostatin receptor subtype 4 (SSTR4) gene has emerged as a significant focus in the investigation of mental health disorders, including schizophrenia, depression, and bipolar disorder, with research implicating its involvement in their pathogenesis (Berent et al., 2017; Zhang et al., 2020; Adamcyzk et al., 2021).