SLC6A1 and schizophrenia: Enzymes related to GABA-ergic neurotransmission, such as glutamic acid decarboxylase (GAD)67 and GABA transporter (GAT)1, are consistently reported to be decreased in patients with schizophrenia.57 A large postmortem study involving 240 controls of all age categories and 31 patients with schizophrenia observed that development and maturation in the prefrontal cortex and the hippocampus is characterized by progressive switches in expression from GAD25 to GAD67 and from NKCC1 to KCC2.