For instance, mGluR2/3 was increased in PFC and hippocampus in the mice reared under isolated conditions (Kawasaki et al. 2011) and in the postmortem PFC of depressed patients (Feyissa et al. 2010), suggesting that elevated function of mGluR2/3 might be the etiological hallmark of depression. Here, GRM2 is linked to major depressive disorder.