Rare genetic variants in SLC12A5 (encoding KCC2) that decrease the KCC2-mediated Cl– extrusion have been linked to autism (R952H and R1049C) and schizophrenia (R952H) (Merner et al., 2015) and a gain of function missense variant in SLC12A2 (encoding NKCC1; Y199C) has been reported in a large cohort of schizophrenic patients (Merner et al., 2016). Here, SLC12A5 is linked to schizophrenia.