Reconciling the differences between the King et al. (1998) and Simms et al. (2002) factor models of PTSD Mark Shevlin, Orla McBride *, Cherie Armour, Gary Adamson School of Psychology, University of Ulster Magee Campus, Northland Road, Co. Londonderry, BT48 7JL, Northern Ireland 1. Introduction Posttraumatic stress disorder (PTSD) was first introduced to the Diagnostic and Statistical Manual of Mental Disorders (DSM) in the third edition (DSM-III: American Psychiatric Association, 1980). Since its initial inclusion the symptom groupings within the diagnostic criteria have undergone a number of changes and are represented in the current edition, DSM-IV (American Psychiatric Association, 1994), in terms of three symptom factors. The symptom factor of Re-experiencing is measured by five symptoms (B1–B5), the Avoidance/Numbing factor is measured by seven symptoms (C1–C7) and the Hyperarousal factor is measured by five PTSD symptoms (D1–D5). Factor analytic support for the three-factor model proposed by the DSM-IV has been limited to a single study (Cordova, Studts, Hann, Jacobsen, & Andrykowski, 2000). It is noteworthy, however, that post-hoc modifications were required for the DSM-IV model of PTSD to fit the data adequately. Indeed, many factor analytic studies have proposed that alternative two or four-factor structures provide better explanations of the underlying dimen- sionality of PTSD (Asmundson et al., 2000). Prior to the inclusion of PTSD in the DSM-III, Horowitz (1979) proposed a two-factor model representing an individual’s response to a traumatic event. The theoretical proposal of a two-factor model was supported further by the work of Horowitz, Alvarez, and Wilner (1979) who developed the Impact of Event Scale (IES) to measure the two symptom groups of Intrusion and Avoidance. Researchers employ- ing both exploratory and confirmatory factor analytic procedures have found support for the two-factor structure (Hodgkinson & Joseph, 1995; Joseph, Williams, Yule, & Hodgkinson, 1993; Shevlin, Hunt, & Robbins, 2000; Zilberg, Weiss, & Horowitz, 1982). Multiple factor analytic studies have concluded that the best representation of the underlying structure of PTSD lies with a four- factor model. The four-factor models proposed by King, Leskin, King and Weathers (1998) and Simms, Watson and Doebbeling (2002) have received the majority of support within the literature to date. The major difference between the King et al. (1998) and the DSM-IV models of PTSD is that the former separates Avoidance into two factors, whilst retaining the symptom groupings of Re- experiencing (B1–B5) and Hyperarousal (D1–D5). These two factors were labeled as Avoidance (C1–C2) and emotional Numbing (C3–C7). Using data from a sample (n = 524) of military veterans who were assessed via the Clinician Administered PTSD Scale (CAPS: Blake et al., 1990), the new four-factor King et al. (1998) model was compared to three alternative PTSD models including the DSM-IV model. Results from the confirmatory factor analysis (CFA) suggested that the new four-factor model was superior to the other models. Subsequent factor analytic studies Journal of Anxiety Disorders 23 (2009) 995–1001 ARTICLE INFO Article history: Received 9 March 2009 Received in revised form 10 June 2009 Accepted 1 July 2009 Keywords: PTSD DSM-IV Confirmatory factor analysis NESARC ABSTRACT Much of the debate surrounding the dimensionality of PTSD relates to three specific Hyperarousal symptoms (D1–D3) and whether they are appropriate indicators of one of two broad constructs that constitute PTSD: Dysphoria or Hyperarousal. This study addressed this issue by testing a series of confirmatory factor models to determine which factor, or factors, these symptoms measured the strongest. Data from individuals who satisfied the conditions for Criterion A of the diagnostic criteria for a DSM-IV diagnosis of PTSD (n = 12,467) in the 2004–2005 NESARC were used in the analysis. The results revealed that the D1–D3 symptoms were not clear indicators of either factor, but measured both Dysphoria and Hyperarousal. Two symptoms, however, loaded more highly on the Dysphoria, rather than Hyperarousal, factor. The present findings lend support to the factor model proposed by Simms et al. [Simms, L. J., Watson, D., & Doebbeling, B. N. (2002). Confirmatory factor analyses of posttraumatic stress symptoms in deployed and non-deployed veterans of the Gulf War. Journal of Abnormal Psychology, 111, 637–647] but also question the use of symptoms that are not unique indicators of specific factors. ß 2009 Elsevier Ltd. All rights reserved. * Corresponding author. Tel.: +44 28 71 375619; fax: +44 28 71 375367. E-mail address: o.mcbride@ulster.ac.uk (O. McBride). Contents lists available at ScienceDirect Journal of Anxiety Disorders 0887-6185/$ – see front matter ß 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.janxdis.2009.07.001