Although society may take a dim view of forgetting, doing so could have a"
silver lining"—helping shield a person traumatized by an
event from developing posttraumatic stress disorder (PTSD).
This notion is suggested by a study conducted by Israeli researchers and
published in the May American Journal of Psychiatry.
When a person experiences a traumatic event, he or she is known to be more
likely to develop PTSD if certain risk factors are present, for example,
preexisting psychiatric illness or physical injury. Several studies have also
suggested that recalling the distressing event might be a risk factor for the
disorder as well. So Ehud Klein, M.D., chair of psychiatry at Rambam Medical
Center in Haifa, Israel, and colleagues conducted a study to determine whether
this is the case.
They enrolled 120 individuals who had sustained head injuries and were
treated for their injuries at the Rambam Medical Center. Most of the injuries
were mild and occurred in traffic accidents.
Each subject was evaluated within 24 hours of the injury with the Memory of
Traumatic Event Questionnaire, which these researchers had developed, they
noted, since no such tool was available at the time of the study. This
nine-item, self-report instrument asked about a subject's memory of the event;
where the event took place; who was involved; when it occurred; sights,
sounds, and odors associated with the event; things the subject remembered
saying during or after the event; and things other people said during or after
After the initial assessment, subjects were then assessed one week, four
weeks, and six months later for PTSD symptoms. Two instruments were used in
the follow-ups—the Clinician-Administered PTSD Scale and the
Posttraumatic Stress Scale.FIG1
The investigators then used the results to determine how well subjects
recalled the excruciating events they had experienced and whether their recall
could be linked with their subsequent development of PTSD.
Within 24 hours after injury, the researchers found, 62 (52 percent) of the
subjects had no memory of the event; 47 (39 percent) had a very good memory of
the event, and 11 (9 percent) had a vague memory of the event. Thus, a bimodal
distribution was evident (see chart). Consequently, a categorical approach was
taken, with participants divided into two groups, with the median of the
questionnaire scale used as the cutoff point. Thus, the subjects were referred
to as either "having memory of the traumatic event" or"
having no memory of the traumatic event." Accordingly, 55 (45
percent) subjects had memory of the traumatic event, and 65 (55 percent)
subjects had no memory of it.
Moreover, of the 65 subjects who had no memory of the event, four developed
PTSD, compared with 13 of the 55 subjects with memory of the event—a
highly significant difference.
"The central finding of our study," the researchers concluded,"
is that memory of a traumatic event is positively associated with the
risk for development of PTSD, while lack of memory of a traumatic event
decreases the risk and might, in fact, play a protective role. Thus, along
with other factors, such as history of previous trauma, previous psychiatric
morbidity, and physical injury, memory of a traumatic event appears to be
another risk factor for PTSD."
Their finding also has a practical implication, the scientists pointed out
in their report. Asking patients whether they can recall the event that
traumatized them may help identify those at risk for PTSD.
Their results, they added, likewise imply that "`deliberate'
disruption of the memory of the traumatic event might prove therapeutically
beneficial." In fact, he and his team are now investigating whether it
is possible to facilitate abolition of troubling memories by pharmacological
means, Klein told Psychiatric News. And if it is possible, he said,"
we will then study the potential therapeutic benefit of such
In view of their finding that recall of a traumatic event may promote
development of PTSD, Klein and his colleagues question whether therapies that"
elicit traumatic memories as part of the recovery
process"—such as exposure therapy—may be counterproductive
in some cases. Nonetheless, a number of studies have found that exposure
therapy can help patients with PTSD.
The study was funded by an internal grant from the Rambam Medical
The report, "Does Memory of a Traumatic Event Increase the
Risk for Posttraumatic Stress Disorder in Patients With Traumatic Brain
Injury? A Prospective Study," is posted online at<http://ajp.psychiatryonline.org/cgi/content/full/162/5/963>.▪
Am J Psychiatry2005162963