Several lines of evidence suggest that cytokines are associated with animal and human aggression [78]–[80] and IL-6 was causally linked to aggression in mice by gene knockout evidence [31]. Our analyses of males whose level of aggression were followed for a 22 year period revealed an association between cytokine levels in plasma and chronic physical aggression: young adult men with a history of chronic physical aggression during childhood have lower baseline concentrations of two pro (IL-1α, IL-6 and IL-8) and two anti (IL-4 and IL-10) -inflammatory cytokines than comparable young adult men without a history of chronic physical aggression during childhood [32]. Here we show data that is consistent with the hypothesis that DNA methylation could be part of the mechanisms responsible for differences in cytokine levels in the chronic aggression group. Indeed, we found differentially methylated regions to associate with CPA in both the cytokine loci as well as in their transcription factors loci analyzed. Some of these differentially methylated regions found in IL-6, IL-4, IL-10, STAT6 and NFkB were located in known regulatory regions whereas others, to our
