GAD1 and schizophrenia: Collectively, these studies, along with several reports of alterations in patients’ cortical levels of histone modifying enzymes, and the observation that therapeutic doses of the mood stabilizer valproate act as a histone deacetylase (HDAC) inhibitor in schizophrenia cases [12], suggest that risk factors for schizophrenia could impact their deteriorating effects on the brain through histone modifications that influence the transcriptional state of genes, such as GAD67, associated with the disorder.