Posttraumatic stress disorder (PTSD) is thought to be a distress-based disorder in hierarchical models (Watson, 2005). Its symptoms were shown to fall on four factors (Intrusions, Avoidance, Dysphoria, and Hyperarousal) by Simms, Watson, and Doebbeling (2002). Intercorrelations among the four ranged from .43 to .61, indicating substantial unshared variance in each factor. King, Leskin, King, and Weathers (1998) also found that a four-factor model (Reexperiencing, Effortful Avoidance, Emotional Numbing, and Hyperarousal) fit their 17-symptom clinical interview better than did any other model, including a single-factor model or a hierarchical model, in which an overall PTSD factor was thought to underlie the four factors. There is thus reason to question whether PTSD is best considered to be a theoretically coherent psychological entity. Clearly, identical PTSD symptom counts can refer to different symptom pictures. It may not be in patients' best interests to assign them a diagnosis that lacks clear meaning.
