Evaluating the dimensionality of PTSD in a sample of OIF/OEF veterans.

Both categorical and dimensional models of mental disorders, including posttraumatic stress disorder (PTSD), are useful for diagnostic and heuristic purposes; however, few empirical studies have compared categorical and dimensional models of PTSD side-by-side or compared these models to a hybrid (dimensional and categorical) model. In the present study, the dimensionality of PTSD was examined by fitting latent profile analytic, confirmatory factor analytic, and factor mixture models in 271 Operation Iraqi Freedom/Operation Enduring Freedom veterans 6 months after return from deployment. Latent profile analysis was used to identify subgroups of individuals with similar PTSD symptom profiles and predictors of subgroup membership, confirmatory factor analysis was used to identify the underlying continuous structure of PTSD in this sample, and factor mixture modeling was used to test whether a hybrid categorical and continuous model of PTSD best fit our sample. A factor mixture model consisting of a 4-factor dysphoria model of PTSD with 2 classes characterized by low and moderate symptom severity was the best-fitting model. Dissociation and deployment concerns emerged as significant predictors of membership in the moderate symptoms class. Implications for PTSD diagnostic conceptualization and treatment planning are discussed.