Recently, HDAC inhibitors also have been explored as potential therapeutic agents in the treatment of psychiatric disorders, including stress-related disorders and addiction, and have become an important focus of research in the neuroscience field (Covington et al. 2009; Kumar et al. 2005; Pandey et al. 2008a; Renthal and Nestler 2008; Tsankova et al. 2007). Here, HDAC9 is linked to psychiatric disorder.