The relation between memory of the traumatic event and PTSD: Evidence from studies of traumatic brain injury

Objective: This paper focuses on the relation between memory and posttraumatic stress disorder (PTSD). More specifically, it addresses the debate regarding the role of memory of the traumatic event in the development of PTSD. Traumatic brain injury (TBI) is used as a naturally occuring model for traumatic exposure that is often associated with memory impairment. Method: We present a critical review of the literature on studies assessing the relation between TBI and PTSD, with a focus on memory of the traumatic event as a critical factor. We also discuss results from recent studies conducted by our group. Results: The literature review offers an inconclusive picture wherein a significant proportion of the studies indicate that PTSD and TBI are mutually exclusive, especially in individuals who exhibit lack of memory for the traumatic event. This finding supports the possibility that lack of memory may protect against the development of PTSD. However, some studies show that PTSD does occur in patients with head injury, suggesting that PTSD may develop in TBI survivors - even in those who cannot remember the traumatic event. Generally speaking, though, the overall balance of the findings (including our own findings) seems to support the possibility that, in subjects with TBI, impaired memory of the traumatic event is associated with reduced prevalence of PTSD. Conclusions: The suggestion that amnesia regarding the traumatic event may protect against the development of PTSD has both theoretical and practical importance. This review focused on the case of trauamtic brain injury as a model for impaired memory for the traumatic event. However, it still remains to be proven that the conclusions based on these findings are generalizable beyond the case of TBI. While some patients with posttraumatic amnesia do develop PTSD despite lack of memory for the traumatic event, the majority of those who lack memory for the event seem to be protected from developing the disorder. Nevertheless, based on this assumption, we suggest that pharmacologic disruption of newly acquired - or even old - traumatic memories, which has been shown to be possible in animals, might therapeutically benefit trauma survivors.