Verbal memory is partially dependent on a region of the brain called the hippocampus. Studies have shown that, in animals, stress can lead to cells dying in this area and some studies have shown a decrease in the volume of the hippocampus, together with memory problems in people suffering from post-traumatic stress disorder (PTSD). PTSD can also involve dysfunctional cognition such as an overly negative appraisal of the traumatic event ('wasn't it dreadful' rather than 'thank goodness I survived'), intrusive thoughts, worry, self-punishment, loss of control and lack of self-confidence. A study of 89 people in Germany compared people who had suffered no trauma, those who had suffered a recent trauma but were yet to develop PTSD and those suffering from PTSD. The researchers found no differences in verbal memory between any of the groups. The recent trauma victims hardly differed from the controls in terms of dysfunctional thought processes but those suffering from PTSD showed more negative appraisal, worry, self-punishment and loss of control than the other groups. Within the group of people who had recently suffered a trauma negative appraisals grew the longer it had been since the original trauma.
Elsesser, Karin and Sartory, Gudrun - Memory performance and dysfunctional cognitions in recent trauma victims and patients with post-traumatic stress disorder Clinical Psychology and Psychiatry November-December 2007, 14(6), 464-474