Genetic association studies also demonstrate that genetic variants of the genes encoding PACAP or PAC1 are associated with schizophrenia, and the risk single nucleotide polymorphism (SNP) for the PACAP gene could be relevant to reduced hippocampal volume and/or poor memory performance, which are both neurobiological traits related to the risk for development of schizophrenia (Hashimoto et al., 2007). This evidence concerns the gene ADCYAP1R1 and schizophrenia.