A number of studies have analyzed AUD-associated DNA methylation changes using DNA methylation analysis approaches that vary in genomic coverage and resolution. Global DNA methylation assays, based on examination of DNA methylation status of repetitive elements (such as Alu and LINE-1), are less expensive but DNA methylation alterations in specific genes or regions are unknown. Regional DNA methylation assays, which require several steps including bisulfite treatment, PCR amplification, and sequencing, are often time consuming and less efficient if multiple regions of interests (often promoter regions of genes) need to be investigated. Genome-wide DNA methylation assays, primarily based (so far) on two types of DNA methylation microarrays (27 and 450K) from Illumina, just probe a small fraction of CpGs in the human genome. To address these issues, Illumina has released an improved DNA methylation array, that is, the Infinium MethylationEPIC BeadChip, which covers more than 850K CpGs across the genome. Additionally, whole genome bisulfite sequencing (WGBS) (or bisulfite treatment of DNA followed by high-throughput sequencing) has been shown to be an important method for studying DNA methylation at single-base resolution,93 and
