DNA Methylation as a Mediator of Cardiovascular Disease Risk in Relation to PTSD Severity: Identification of Potential Epigenetic Biomarkers.

Post-traumatic stress disorder (PTSD) is associated with increased cardiovascular disease (CVD) risk, yet the epigenetic mechanisms underlying this link remain unclear. We investigated whether DNA methylation (DNAm) within Conserved Regions of Systemic Interindividual Variation (CoRSIVs), genomic regions showing stable within-individual, but variable between-individual methylation, mediates the association between PTSD symptom severity (PTSS) and CVD. We analyzed blood-derived DNAm from three cohorts (DNHS: discovery; GTP and NHS: replication), focusing on 7,694 CoRSIV CpGs profiled with the Illumina MethylationEPIC BeadChip. Logistic regression related CpGs to PTSS and CVD, adjusting for demographic and trauma-related covariates. CpGs nominally associated (p<0.05) with both PTSS and CVD in DNHS were then tested using causal mediation analysis. In DNHS, 27 CpGs were nominally associated with both PTSS and CVD, with seven showing nominal mediation (p<0.05). Across cohorts, six of these seven displayed mediation effects in a consistent direction in at least one replication cohort, and three CpGs showed concordant mediation directions across all three cohorts. Notably, cg07941916 (C5orf56/IRF1-AS1) and cg20545458 (intergenic) exhibited positive mediation in DNHS with the same direction in GTP, implying that higher PTSS is associated with methylation changes that correspond to higher CVD risk, whereas all mediation effects in NHS were negative, consistent with its healthier, lower-risk profile. These loci map to immune and inflammatory pathways, alongside other mediators annotated to neuronal/stress-aging and autonomic processes. Overall, DNAm variation within CoRSIVs may partially mediate PTSD-related CVD risk and nominates specific CpGs as hypothesis-generating epigenetic biomarkers that require validation in larger, ancestrally diverse longitudinal cohorts.