Context The nature of the relationship of dissociation to posttraumatic stress disorder (PTSD) is controversial and of considerable clinical and nosological importance. Objective To examine evidence for a distinct subtype of PTSD characterized by high levels of dissociation. Design A latent profile analysis of cross-sectional data from structured clinical interviews indexing DSM-IV symptoms of current PTSD and dissociation. Setting VA Boston and New Mexico VA Healthcare Systems. Participants 492 Veterans and their intimate partners, all of whom had histories of trauma. Participants reported exposure to a variety of traumatic events including combat, childhood physical and sexual abuse, partner abuse, motor vehicle accidents, and natural disasters, with most participants reporting exposure to multiple types of traumatic events. Forty-two percent of the sample met criteria for a current diagnosis of PTSD. Main Outcome Measures Item-level scores on the Clinician Administered PTSD Scale. Results A latent profile analysis suggested a three class solution: a low severity subgroup, a high PTSD severity subgroup characterized by elevations across the 17 core symptoms of the disorder, and a small but distinctly dissociative subgroup that comprised 12% of individuals with a current diagnosis of PTSD. The latter group was characterized by severe PTSD symptoms combined with marked elevations on items assessing flashbacks, derealization, and depersonalization. Individuals in this subgroup also endorsed greater exposure to childhood and adult sexual trauma compared to the other two groups suggesting a possible etiologic link with the experience of repeated sexual trauma. Conclusions Results support the subtype hypothesis of the association between PTSD and dissociation and suggest that dissociation is a highly salient facet of posttraumatic psychopathology in a subset of individuals with the disorder.

We describe the results of the first genome-wide association study of PTSD performed using trauma-exposed white non-Hispanic participants from a cohort of veterans and their intimate partners (295 cases and 196 controls). Several SNPs yielded evidence of association. One SNP (rs8042149), located in the retinoid-related orphan receptor alpha gene (RORA), reached genome-wide significance. Nominally significant associations were observed for other RORA SNPs in two African American replication samples—one from the veteran cohort (43 cases and 41 controls) and another independent cohort (100 cases and 421 controls). However, only the associated SNP from the veteran African American replication sample survived gene-level multiple testing correction. RORA has been implicated in prior GWAS studies of psychiatric disorders and is known to play an important role in neuroprotection and other behaviorally-relevant processes. This study represents an important step towards identifying the genetic underpinnings of PTSD.