GAD1 and schizophrenia: In contrast, smaller genetic studies have shown that single nucleotide polymorphisms (SNPs) and loss-of-function mutations in the GAD1 gene were involved in GAD67 expression levels and schizophrenia (Addington et al., 2005; Straub et al., 2007; Du et al., 2008; Hyde et al., 2011; Giacopuzzi et al., 2017; Magri et al., 2018).