Comparing posttraumatic stress disorder's symptom structure between deployed and nondeployed veterans.

We tested two empirically validated 4-factor models of posttraumatic stress disorder (PTSD) symptoms using the PTSD Checklist: King, Leskin, King, and Weathers' (1998) model including reexperiencing, avoidance, emotional numbing, and hyperarousal factors, and Simms, Watson, and Doebbeling's (2002) model including reexperiencing, avoidance, dysphoria, and hyperarousal. Our aim was to determine which fit better in two groups of military veterans: peacekeepers previously deployed to a war zone (deployed group) and those trained for peacekeeping operations who were not deployed (nondeployed group). We compared the groups using multigroup confirmatory factor analysis. Adequate model fit was demonstrated among the nondeployed group, with no significant difference between King et al.'s (1998) model (separating avoidance and numbing) and Simms et al.'s (2002) similar model involving a dysphoria factor. A better fitting factor structure consistent with Simms et al.'s (2002) model was found in the deployed group. Comprehensive measurement invariance testing demonstrated significant differences between the deployed and nondeployed groups on all structural parameters, except observed variable intercepts (thus indicating similarities only in PTSD item severity). These findings add to researchers' understanding of PTSD's factor structure, given the revision of PTSD that will appear in the forthcoming 5th edition of the Diagnostic and Statistical Manual of Mental Disorders (American Psychiatric Association, 2010)--namely, that the factor structure may be quite different between groups with and without exposure to major traumatic events.