Consistency of Memory Among Veterans of Operation Desert Storm

To The Editor: The recent article by Steven Southwick, M.D., and colleagues (1) on the consistency of memory for combat-related traumatic events among veterans of Operation Desert Storm raises a number of issues that we believe deserve further investigation. Perhaps the most important of these is the determination of which memory report is more accurate. This is the key to understanding whether it is the case that traumatized individuals initially suffer acute dissociation and memory disturbance and later recover true memories or, conversely, that their initial memories are veridical and complete and that distortions, pseudo­memories, or both creep in with time and postevent information. Given that it was not possible for Southwick et al. to assess the accuracy of recall in their study, future research should identify traumatic situations for which accuracy can be verified and conduct multiple assessments of the recall of these traumatic events. In evaluating the accuracy of recall over time, such research should distinguish “false negatives” (i.e., failing to recall traumatic events that were experienced, possibly because of dissociation) from “false positives” (i.e., reporting traumatic events that were not experienced, possibly because of subsequent exposure to information about the traumatic event).

The distinction between memory recall and memory report may also be a factor in interpreting at least some of the findings of Southwick et al. For example, one might view endorsement of an item such as “extreme threat to your personal safety” (the item most often changed by subjects) as a judgment about the characteristics of the event rather than as a statement about accessibility of the memory for the event. The fact that subjects did not endorse this item at one time or another does not necessarily mean that they did not remember the event at time 1 or had forgotten it by time 2 (i.e., recall changes). It could mean, instead, that subjects were able to access the memory at both times but thought differently about the memory’s meaning at different times; consequently, their reports, but not their recall, of the event changed.

Another issue worth pursuing in future research is just what aspect of memory is implicated in these changes. Because no control (nontraumatic) memory items were included in the questionnaire in this study, we do not know whether these findings are specific to traumatic memories of patients with PTSD or whether they are more general and apply to all memories of PTSD patients. This question is especially intriguing given that there is some evidence of other non-trauma-related memory impairment in this population (2).

Future investigations should help resolve the issues of the timing, the mechanisms, and the meaning of changes in recall of traumatic experience.