The fallacy of ex-consequentia reasoning and the persistence of PTSD.

Many individuals experience psychological distress after a potentially traumatic event, but only a minority develops chronic posttraumatic stress disorder (PTSD). According to the cognitive model of Ehlers and Clark (Behaviour Research and Therapy 38 (2000) 319), chronic PTSD results from distorted beliefs about the trauma or its sequelae. Given the availability of disconfirming information, why do such distorted beliefs persist? A recent promising line of research focuses on the "ex-consequentia" reasoning fallacy: "if I feel anxiety, there must be danger". Ex-consequentia reasoning may start a vicious circle in which subjective fear responses are used to erroneously validate thoughts of impending doom, which intensifies distress, etc. In other words, false alarms are not recognized and irrational beliefs are maintained. We previously found that other anxiety patients (Behaviour Research and Therapy 33 (1995) 917) and PTSD patients (Behaviour Research and Therapy 39 (2001) 1139) show ex-consequentia reasoning, that is, they appear to believe that anxiety symptoms imply the presence of danger. Interestingly, this was not restricted to situations relevant to the individual's anxiety disorder. Tentative data suggest that ex-consequentia reasoning is causally involved in the persistence of PTSD and anxiety disorders. These are presented and possible underlying mechanisms are discussed.