it is difficult to obtain a homogeneous sample (where subjects are diagnosed only with AUDs and there is no comorbidity) for AUD study; and perhaps most importantly; (iii) for epigenetic studies, we would prefer to study the most relevant tissue. This can be easy for investigations of cancer epigenetics as the tumor tissue of interest is likely to be accessible. To understand the epigenetics of AUDs, we would prefer to study brain tissue. However, brain tissue samples from live AUD subjects are usually inaccessible. In spite of these difficulties, epigenetic studies (particularly DNA methylation studies) on AUDs are advancing quickly making use of those tissues that are available—blood and saliva from living subjects, and postmortem brain from deceased subjects. This review highlights the major findings on the association of DNA methylation and AUDs in human subjects as well as the most important and interesting future directions the research field may take in the near future.
