It is noteworthy that HDAC and DAXX show increased expression in schizophrenia, while PAX5 and Runx2 show decreased transcripts in bipolar disorder, two disorders in which parallel reductions in the expression of GAD67 have also been reported in a layer of the hippocampus that exclusively contains neurons of the GABAergic type [3]. This evidence concerns the gene HDAC9 and bipolar disorder.