Factor structure of posttraumatic stress disorder (PTSD) in Australian Vietnam Veterans: confirmatory factor analysis of the Clinician-Administered PTSD Scale for DSM–5

Abstract

Introduction: The Diagnostic and Statistical Manual of Mental Disorders (5th ed.; DSM–5) brought a change to the symptom clusters of posttraumatic stress disorder (PTSD). In line with the DSM–5 changes, an updated version of the Clinician-Administered PTSD Scale (CAPS–5) was released. The CAPS–5 is considered to be the gold-standard measure of PTSD; however, examinations of the psychometric properties and optimal factor structure of this scale are underrepresented in PTSD studies. Methods: This study used confirmatory factor analysis (CFA) to assess the factor structure of the CAPS–5 using a sample of 267 male Australian Vietnam Veterans. Models drawn from the PTSD CFA literature were used to test the underlying dimensions of PTSD: the four-factor DSM–5 model, six-factor externalizing behaviour and anhedonia models, and seven-factor hybrid model. Results: The results found that the DSM–5 model showed slightly less than adequate fit (comparative fit index [CFI] = 0.90, Tucker–Lewis index [TLI] = 0.88, root mean square error of approximation [RMSEA] = 0.064), however, other models showed acceptable fit. The anhedonia model provided a significantly better fit than the other models (CFI = 0.92, TLI = 0.90, RMSEA = 0.059). Discussion: Overall, the results supported the anhedonia model. This result may indicate that the underlying dimensions of PTSD in Australian Vietnam Veterans may best be represented by six distinct factors.