The class-dimensional structure of PTSD before and after deployment to Iraq: Evidence from direct comparison of dimensional, categorical, and hybrid models.

The assumption of specific etiology in posttraumatic stress disorder (PTSD) differentiates the disorder from most other psychiatric conditions. A 'risky test' of the assumption of specific etiology and resultant trauma-related symptom dimensions was conducted through structural modeling of PTSD symptoms in soldiers before (N=522) and after (n=423) a combat deployment to Iraq. If PTSD represents a discrete diagnostic entity that emerges after trauma exposure, we hypothesized either the number of latent classes should increase from pre- to post-deployment or symptom dimensions should qualitatively distinguish affected from unaffected classes following trauma exposure. Comparison of latent structural models revealed best fitting hybrid models for PTSD and depression with strong invariance of symptom dimensions across classes both before and after deployment and only quantitative (i.e., severity) differences between classes. These findings suggest PTSD is generally well-conceptualized as a dimensional syndrome worsened but not necessarily elicited by trauma exposure.