DRD2 and major depressive disorder: Still, a growing number of analyses based on leukocyte-derived DNA methylation in psychiatric disorders exist, including a study of the DRD2 5′-regulatory region in sib pairs discordant for schizophrenia (Zhang et al. 2007), a functional study of the SLC12A6 promoter (Moser et al. 2009), and a methylation-sensitive representational difference analysis of lymphoblastoid cells derived from monozygotic twins noted above (Kuratomi et al. 2008), the report on BDNF methylation in unipolar depression noted above (Fuchikami et al. 2011), and the investigation of BD (D'Addario et al. 2012).