An investigation of whether patients with post-traumatic stress disorder overestimate the probability and cost of future negative events.

This study compared estimations of the probability and cost of negative events occurring made by patients with post-traumatic stress disorder (PTSD) (n=43), patients with other anxiety disorders (n=29) and non-patients' (n=35). Prior to treatment PTSD patients overestimated the probability and cost of all types of traumatic events occurring relative to non-patients, and overestimated the probability and cost of the specific type of traumatic event that they had been traumatized by relative to the anxious controls as well as non-patients. These judgment biases were specific to traumatic events and did not generalise to all negative events. PTSD patients' estimations of the probability and cost of traumatic events were significantly reduced following treatment, and were no longer significantly different from those of non-patients. Results suggest that patients with PTSD show specific judgment biases in the estimation of probability and cost, which can be successfully modified by cognitive therapy.