There is some controversy in the scientific literature regarding post-traumatic stress disorder and amnesia. Some research seems to show that it is specific memories of the traumatic event that precipitates the re-experiencing of the trauma.
This study looked at 282 patients diagnosed with traumatic brain injury (TBI) at an outpatient traumatic brain injury clinic. Motor vehicle accidents were responsible for 66% of the injuries, while pedestrian accidents, assaults, and falls accounted for the majority of the rest. Most of the subjects in the study were assessed within 2 months of their initial injury, on average.
The purpose of the study was to look at the relationship between traumatic brain injury (TBI), posttraumatic amnesia (PTA), and posttraumatic stress disorder (PTSD). Normally, PTSD is based upon intrusive recall of traumatic data, and the question was raised whether TBI and the duration of posttraumatic amnesia (PTA), which can hinder the recall of an injurious event, affect the occurrence of PTSD symptoms.
The study sample was divided into four groups, based on the duration of their posttraumatic amnesia (PTA) according to the criteria of Russell and Smith.
The authors of the study note that this is one of the first to look at the full spectrum of head injury severity, and to look at TBA and PTSD symptoms based on the length of duration of PTA. Normally, increasing severity of amnesia correlates with the severity of the brain injury and can affect eventual patient outcomes.
The authors found that PTSD symptoms (measured with the Impact of Event Scale, a self-report measure of PTSD intrusive and avoidant symptoms) diminished when the PTA exceeded one hour.
"In a sample of head-injured patients assessed within a couple of months of injury and stratified for the severity of head injury on the basis of duration of PTA, symptoms of PTSD occurred in all groups. However, when PTA extended beyond one hour, symptoms of re-experiencing the traumatic event (intrusive phenomena) and avoidant behavior were endorsed significantly less often…in addition, whether or not these phenomena in the more seriously injured (i.e., PTA>1 week) represent the historical ‘truth’ or an embellishment or confabulation of what occurred, as some have suggested, cannot be answered here."
While PTSD symptoms decreased with PTA duration of more than one hour, General Health Questionnaire scores (GHQ) remained constant. This 28-item test recorded symptoms of anxiety and depression and remained constant regardless of the length of PTA.
The authors noted, "The divergence of PTSD-type symptoms and GHQ scores with increasing PTA makes it unlikely that emotional factors alone were responsible for patients endorsing recollections of their trauma and suggests that additional theories must be invoked to explain this aspect of PTSD symptom development our data help dispel the notion that for PTSD to develop in the context of PTA, the 'amnesia' must represent a subject's psychological repression of the traumatic event. The association of unequivocal brain damage with PTSD-type symptoms, therefore, suggests that repression is applicable only to patients with mild head injury without a loss of consciousness or with the briefest alteration in consciousness who go on to develop PTSD reactions without recall for what occurred."
The study did conclude that PTSD symptoms can occur across the full range of head injury severity, though, and should receive attention when treating patients.