The structure of posttraumatic stress disorder symptoms in combat veterans: a confirmatory factor analysis of the impact of event scale.

There has been controversy over the most appropriate way to define symptom clusters for posttraumatic stress disorder (PTSD). We tested the factor structure of the Impact of Event Scale (IES) in a sample of 195 male combat veterans with chronic PTSD by using confirmatory factor analysis. The two-factor model including Intrusion (i.e., unwanted memories of the event) and Avoidance (i.e., attempts to avoid reminders and numbing of emotional responsiveness) deviated significantly from good fit. However, a four-factor model, including Intrusion and Effortful Avoidance subscales, as well as Sleep Disturbance and Emotional Numbing subscales, fit significantly better. Correlations with other PTSD measures are explored and implications for the conceptualization of PTSD are discussed.