A factor analysis of posttraumatic stress disorder symptoms using data pooled from two venlafaxine extended-release clinical trials

BACKGROUND: Confirmatory factor analysis (CFA) of Diagnostic and Statistical Manual of Mental Disorders (Fourth Edition) (DSM-IV) three-factor posttraumatic stress disorder (PTSD) diagnostic criteria was conducted to determine fit for this patient population. An exploratory factor analysis (EFA) of alternate symptom structures was planned to identify symptoms that cluster in this population. The response of symptom factors to treatment with venlafaxine extended release (ER) was explored. METHODS: Baseline 17-item Clinician-Administered PTSD Scale (CAPS-SX(17)) data were pooled from patients enrolled in two double-blind, randomized, placebo-controlled trials. The CFA was conducted using maximum likelihood and weighted, least-squares factor extraction methods. The EFA was performed using a polychoric correlation covariance matrix and Pearson correlation matrix. RESULTS: Data from a pooled population of 685 patients (venlafaxine ER: n = 339; placebo: n = 346) were analyzed. CFA rejected the DSM-IV three-factor structure. The EFA identified a different three-factor structure as the best fit: factor 1 included reexperiencing symptoms, factor 2 included symptoms of altered mood and cognition, whereas factor 3 comprised avoidance and arousal symptoms. All DSM-IV symptom factors and all factors in the identified three-factor model responded positively to venlafaxine ER treatment. CONCLUSIONS: Data are consistent with literature failing to confirm the three-factor structure of DSM-IV PTSD, and they support the DSM-5 inclusion of a symptom cluster addressing altered mood and cognition in PTSD. The efficacy of venlafaxine ER in reducing a range of symptom clusters in PTSD is consistent with its multiple mechanisms of action.