GAD1 and schizophrenia: GAD1, a gene encoding the GABA synthetic enzyme glutamate decarboxylase 67-kDa (also referred to as gamma aminobutyric acid 67, GAD67), is downregulated in patients with schizophrenia (Fujihara et al., 2015, 2020; Tao et al., 2018), which may contribute to the disinhibition associated with schizophrenia (Volk and Lewis, 2002).