Epigenetic and immune function profiles associated with post-traumatic stress disorder

The biological underpinnings of post-traumatic stress disorder (PTSD) have not been fully elucidated. Previous work suggests that alterations in the immune system are characteristic of the disorder. Identifying the biological mechanisms by which such alterations occur could provide fundamental insights into the etiology and treatment of PTSD. Here we identify specific epigenetic profiles underlying immune system changes associated with PTSD. Using blood samples (n=100) obtained from an ongoing, prospective epidemiologic study in Detroit, the Detroit Neighborhood Health Study (DNHS), we applied methylation microarrays to assay CpG sites from over 14,000 genes among 23 PTSD-affected and 77 PTSD-unaffected individuals. We show that immune system functions are significantly overrepresented among the annotations associated with genes uniquely unmethylated among those with PTSD. We further demonstrate that genes whose methylation levels are significantly and negatively correlated with traumatic burden show a similar strong signal of immune function among the PTSD-affected. The observed epigenetic variability in immune function by PTSD is corroborated using an independent biological marker of immune response to infection, cytomegalovirus—a typically latent herpesvirus whose activity was significantly higher among those with PTSD. These results provide the first report of peripheral epigenomic and CMV profiles associated with mental illness and suggest a new biological model of PTSD etiology in which an externally experienced traumatic event induces downstream alterations in immune function by reducing methylation levels of immune-related genes.