With regards to the GluN2 subunits, one study has reported an increase in GluN2B mRNA in the hippocampus in schizophrenia, with two further studies reporting no change, and no changes have been reported for GluN2A mRNA, or the less expressed 2C and 2D subunits [7,10,12]. Here, GRIN2B is linked to schizophrenia.