GAD1 and schizophrenia: The most consistent findings in post-mortem brain studies of schizophrenia patients are reduced numbers of parvalbumin (PARV)-containing GABAergic interneurons and a decreased expression of the 67-kDa isoform of the GABA-synthesizing enzyme glutamate acid decarboxylase (GAD67) in cerebral cortex and hippocampus (Akbarian et al. 1995; Guidotti et al. 2000; Hashimoto et al. 2003; Lewis et al. 2005).