GRM2 and schizophrenia: It remains possible that in schizophrenia there are localised alterations (e.g. in particular cell populations, or in other brain regions), or changes which occurred prior to the onset of illness, or which are limited to particular phases of the illness (c.f. the possibility that mGlu2/3 agonists are effective early but not late in the disease; Kinon et al., 2015, Krystal and Anticevic, 2015).