Recently, genetic association studies have also shown that genetic variants of the genes encoding PACAP or PAC1 are associated with schizophrenia (Hashimoto et al., 2007), major depressive disorder (Hashimoto et al., 2010), and post-traumatic stress disorder (PTSD) (Ressler et al., 2011). This evidence concerns the gene ADCYAP1 and major depressive disorder.