The third approach, quite different in its goals from the methods described above, is to perform longitudinal or multi-generation epigenetic studies to confirm whether AUD-associated DNA methylation changes are attributable to alcohol consumption, environmental factors, or inherited from parents, or as seems most likely, some combination of these. Longitudinal studies have distinct advantages over cross-section studies (which were applied in most published studies on epigenetics of AUDs). Importantly, longitudinal studies do not need to consider the influence of genetic variation on DNA methylation, and thus, can directly identify the temporal or dynamic DNA methylation changes in individual subjects. It is expected that a longitudinal survey can provide direct evidence that AUD-associated DNA methylation changes are a result of alcohol consumption. To date, only two studies are known to have used the longitudinal DNA methylation study approach to identify DNA methylation changes associated with chronic alcohol consumption. One study analyzed AVP and ANP promoter DNA methylation changes in the peripheral blood of 99 AUD patients on days 1, 7, and 14 of alcohol withdrawal,106 and the another study tracked blood DNA
