A Re-Kindling Process Produces Late-Onset PTSD
Not everyone who experiences trauma develops post-traumatic stress disorder (PTSD) immediately. Researchers are discovering that some people go on to develop symptoms like flashbacks or intrusive thoughts, anxiety, and withdrawal, sometimes after long periods of being asymptomatic. Two studies provide hints about the mechanism of this late-onset (or delayed-type) PTSD.
In an article by Danny Horesh et al. published in the journal Psychiatry Research in 2013, a reported 16.5% of 675 Israeli veterans of the 1982 conflict with Lebanon developed late-onset PTSD after a completely non-symptomatic period. The number of deployments soldiers were sent on and the number of terror incidents they experienced within Israel after the war were correlates of the late-onset PTSD, while continuous post-war employment was a protective factor reducing late-onset PTSD.
In a study of 260 older adults (above age 60) who survived the destruction around Galveston Bay, Texas by Hurricane Ike in 2008, Robert H. Pietrzak et al. reported in the Journal of Psychiatry Research in 2013 that 5.3% developed late-onset PTSD. In this case as well, a greater number of subsequent traumatic and stressful life events (and in particular financial difficulties) was associated with late onset of PTSD. The majority of participants in Pietrzak’s study (78.7 %) had no to few PTSD symptoms, while 16.0% had chronic PTSD symptoms from the outset persisting through assessments at three months and 15 months.
Editor’s Note: These two studies reveal that upon prospective follow-up, a small but substantial group of patients (5–16%) develop a late-onset type of PTSD. Acute onset PTSD has been closely linked to new trauma in adulthood, especially following the occurrence of previous (childhood) traumas. The late-occurring variety of PTSD seems to appear after an incubation period, and appears to be closely associated with the occurrence of new traumatic events during the well interval. These new events may result in a kindling-like effect, where repetition of subthreshold stimuli come to evoke a full-blown episode. PTSD appearing after repeated traumatic experiences may operate in a similar fashion to seizures that gradually emerge following repeated electrical stimulation of the amygdala (i.e. amygdala kindling).
In the fifth issue of the BNN from 2012, we wrote about a process by which traumatic memories go through an initial period of consolidation and then are later re-consolidated. During this reconsolidation process, a window opens five minutes to one hour after active recall of the memory, during which old memories are subject to long-term revision. This extinction of traumatic memories is being used in the treatment of acute PTSD, and therapy involving eye movement desensitization and reprocessing (EMDR) also makes use of these principles through active recall and subsequent reworking of the traumatic memory within the reconsolidation window.
Since the experience of new traumas following an initial severe trauma appears to be related to the development of late-onset PTSD, it may be possible to desensitize the old and new traumatic memories by reworking them in the reconsolidation window after active recall, and thus potentially prevent the development of the late-onset type of PTSD.
