The dimensional structure of posttraumatic stress symptomatology in 323,903 U.S. veterans

There is ongoing debate regarding the optimal dimensional structure of posttraumatic stress disorder symptomatology. A better understanding of this structure has significant implications, as it can provide more refined phenotypic measures for use in studies of the etiology and neurobiology of PTSD, as well as for use as endpoints in treatment studies of this disorder. In this study we analyzed the dimensional structure of PTSD symptomatology, as assessed using the PTSD Symptom Checklist-Military Version in 323,903 Veterans. Confirmatory factor analyses were used to compare two 4-factor models and a newly proposed 5-factor model to the 3-factor DSM-IV model of PTSD symptom dimensionality. To evaluate the external validity of the best-fitting model, we then conducted a structural equation model examining how the symptom dimensions of this model related to diagnoses of depression, anxiety, and substance use disorder. Results indicated that a newly proposed 5-factor 'dysphoric arousal' model comprised of separate re-experiencing, avoidance, numbing, dysphoric arousal, and anxious arousal symptom clusters provided a significantly better fit to the data compared to the DSM-IV and the two alternative four-factor models. External validity analyses revealed that numbing symptoms were most strongly related to diagnoses of depression and substance use disorder, and that dysphoric arousal symptoms were most strongly related to a diagnosis of anxiety disorder. Thus the dimensional structure of PTSD may be best represented by five symptom dimensions. The clinical implications of these results and implications for further refinement of extant PTSD assessment instruments are discussed.