Epigenetic studies of the glutamatergic system in patients with schizophrenia reported differential methylation of the glutamate receptor ionotrophic alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid 2 and 3 and glutamate metabotropic receptors 2, 5, and 8 (Aberg et al., 2012; Kordi-Tamandani et al., 2013; Teroganova et al., 2016). Here, GRM2 is linked to schizophrenia.