AHRR and post-traumatic stress disorder: Individuals with PTSD have increased methylation at a CpG site located in Toll-like receptor 8 (TLR8) (Smith et al., 2011), and decreased methylation at CpG sites located in dedicator of cytokinesis 2 (DOCK2) (Mehta et al., 2017), nuclear factor of activated T-cells (NFATC4) (Hammamieh et al., 2017), IL12B (Bam et al., 2016b) and aryl hydrocarbon receptor repressor (AHRR) (Logue et al., 2020; Smith et al., 2020).