There is increasing interest in exploring the potential role of cross-generational epigenetic effects in mediating the risk of complex phenotypes, including those related to drug addiction and other neuropsychiatric conditions. The results of this study demonstrate that THC exposure before mating can elicit molecular disturbances leading to lasting cross-generational DNA methylation alterations in the NAc of adult, unexposed progeny. These DNA methylation changes were localized to clusters of CpGs occurring at 406 hypermethylated and 621 hypomethylated DMRs across the genome. Importantly, our use of stringent filtering criteria and a sliding-window-based analysis for DMR discovery limited the inclusion of false-positive CpGs. Thus, although on average the observed methylation differences were modest, these sites likely represent robust epigenetic changes given that we required multiple neighboring CpGs within DMRs to exhibit concordant methylation patterns (Table 1; Figure 2). Furthermore, the magnitude of observed methylation differences are likely consistent with those expected from a model of epigenetic cross-generational transmission, and are comparable to what has been observed by epigenome-wide association studies in complex traits (De Jager PL, 2014; Huynh et al, 2014; Pidsley et
