NEGR1 and obesity due to melanocortin 4 receptor deficiency: Although NEGR1 has been recognized as an obesity risk gene (Willer et al., 2009), recent large genome-wide association studies (GWAS) have identified NEGR1 as one of the most significant risk genes for major depressive disorders (MDD) (Howard et al., 2018; Wray et al., 2018).