GRM3 and schizophrenia: Because of the correlations of mGlu3 immunoreactivity with age, pH and PMI, and the fact that these variables differed significantly between controls and cases in the whole sample which would confound their use as covariates (Table 2), we performed our case-control comparisons on a sub-sample (of 63 controls and 46 patients with schizophrenia) which was matched on these variables (a ‘matched’ series; Table 2).