Similarly, serotonin-pathway genes connect depression and obesity: loss-of-function mutations in the appetite-regulating receptor gene HTR2C predispose the individual to hyperphagia and severe obesity, while other serotonergic variants, such as HTR2A polymorphisms, have been associated with postpartum depression [105,106]. The gene discussed is HTR2A; the disease is obesity due to melanocortin 4 receptor deficiency.