Consistency of Traumatic Memories

TO THE EDITOR: We commend Steven M. Southwick, M.D., and colleagues on their empirical investigation of the consistency of retrospective reports of combat-related traumatic events (1). We concur that the field of traumatic stress all too often treats retrospective reports as objective measures of exposure, despite a lack of evidence to support their accuracy. We have conducted similar research and have also found systematic inconsistencies over time in the retrospective accounts of war-zone events among Somalia veterans (2). These findings challenge the validity of the assumption that a significant association between degree of combat exposure and posttraumatic symptoms represents a unidirectional relationship in which exposure predicts posttraumatic stress disorder (PTSD). In addition to emphasizing the need to show caution when using retrospective reports of events as necessarily objective measures of exposure, these studies point to the importance of expanding the simple dose-response theory that depicts the relationship between exposure and symptoms in causal models of PTSD (3).

Dr. Southwick and colleagues appropriately frame their study within the larger context of current debate in the field regarding the accuracy or inaccuracy of traumatic memory. They conclude accurately that their findings “do not support the notion that memory for traumatic events is fixed, indelible, or stable over time.” However, given the enormous attention and furor surrounding issues of recovered memories and false memories, we feel it is important to clarify that neither these findings, nor the findings from our research, speak directly to the issue of recovered memories. As Southwick et al. note, memories of events may have been “repressed” during the first assessment and then recalled for the second one. Conversely, reports of occurrence might have been inflated by symptomatic individuals. Also, Southwick et al. assessed reports of exposure among individuals who were verifiably exposed to a stressful situation. Thus, although these data confirm that the reported frequency and intensity of known exposure may change over time, they do not at all address the issue of whether the occurrence of a potentially traumatic event might be falsely reported by an individual. Finally, a statistical difference in reports of the frequency of events at different time periods does not necessarily correspond to a clinically significant difference in the total impact of exposure to potentially traumatizing events. We hope that researchers will continue careful investigation of the nature of inconsistencies in memory for potentially traumatizing events and the functional impact of these inconsistencies.