Effect of Prolonged Exposure Therapy on PTSD Symptom Severity in Military Personnel

Posted August 24, 2018

Edna Foa, Ph.D., University of Pennsylvania

Edna Foa, Ph.D., University of Pennsylvania

Edna Foa, Ph.D.,
University of Pennsylvania

In 2007, the Department of Defense (DoD) awarded a PTSD Multidisciplinary Research Consortium Award through the Psychological Health and Traumatic Brain Injury Research Program to the South Texas Research Organization Network Guiding Studies on Trauma and Resilience (STRONG STAR) consortium. As of December 2017, STRONG STAR had received over $45 million from the DoD to support infrastructure and projects. Members of the STRONG STAR consortium include civilian, military, and US Department of Veterans Affairs scientists and clinicians who conduct basic science research, preclinical studies, and clinical trials with the goal of identifying, developing, and evaluating the most effective treatments for combat-related post-traumatic stress disorder (PTSD) in active duty Service members and Operation Iraqi Freedom (OIF)/Operation Enduring Freedom (OEF) Veterans. A large proportion of military personnel returning from Iraq and Afghanistan have been and are affected by PTSD, which places substantial psychological and physical stresses on those individuals. Many of the treatment options available have not been tested on active duty military personnel, so there is a compelling need for evidence-based studies examining treatment efficacy in this crucial population.

Dr. Foa, whose project was funded as a partnering award to the STRONG STAR consortium, conducted a randomized clinical trial at Fort Hood, Texas, comparing the effectiveness of massed-prolonged exposure therapy (massed-PE) to traditional spaced-prolonged exposure therapy (spaced-PE), and present-centered therapy (PCT) on PTSD severity. Prolonged exposure therapy is a form of cognitive behavioral therapy that exposes an individual to traumatic memories and can be administered through 10 sessions over 8 to 15 weeks (for spaced-PE) or over 2 weeks (for massed-PE). Traditional spaced-PE has been shown to be effective in civilian and OIF/OEF Veteran populations; however, the protracted duration of this treatment presents scheduling obstacles for active duty personnel, whose military duties rank foremost in their timetables. PCT, also administered over 8 weeks and 10 sessions, is a non-trauma-based approach in which individuals are encouraged to identify and discuss daily stressors. Comparing massed-PE to spaced-PE and PCT in an active duty population, Dr. Foa and her colleagues hypothesized that massed-PE is as effective as spaced-PE and PCT in reducing PTSD symptom severity. If this can be proven, massed-PE could become a viable alternative treatment regimen for active duty Service members, who have limited time to invest in therapy.

In a recently published manuscript in the Journal of the American Medical Association, Dr. Foa described the results of the randomized clinical trial. Three hundred seventy (370) participants were enrolled and randomized to receive either massed-PE, spaced-PE, PCT, or minimal contact (control group). Participants’ PTSD symptom severity and diagnostic status were measured using the PTSD Symptom Scale-Interview (PSS-I) and the PTSD Checklist-Stressor-Specific (PCL-S), where higher scores on both measures indicate greater PTSD severity. PSS-I and PCL-S scores were obtained before and after the treatment period and at 2-week, 12-week, and 6-month follow-ups so as to evaluate improvements, or lack thereof, in PTSD severity. Significant decreases in PSS-I and PCL-S scores were observed in participants receiving massed-PE and spaced-PE after the treatment period and at the 2-week follow-up. These decreases in PSS-I and PCL-S scores were retained up to 6 months after the end of treatment. Similar decreases were observed in the PCT group post-treatment when compared to the spaced-PE group. However, because most of the cohort was comprised of participants with low to moderate baseline PTSD severity on the PSS-I, it was important to determine the efficacy of spaced-PE compared to PCT for participants with severe baseline PSS-I (32 score and above). Spaced-PE participants with severe initial PTSD showed continued reductions in PTSD symptoms during follow-up whereas PCT participants did not. Hence, spaced-PE participants with high baseline PTSD severity had significantly lower at 6-month follow-up than participants in PCT. The number of adverse events, defined as a clinically significant negative change in physical or mental health, was tracked over the course of the study. Although not significantly different, adverse events reported in the massed-PE group were fewer than those reported in the spaced-PE group (96 versus 115, respectively). Importantly, Dr. Foa showed that the dropout rate for each cohort during treatment and at the 6-month follow-up were comparable across all groups. During treatment, the dropout rate of participants receiving massed-PE, spaced-PE, and PCT was 13.6%, 24.8%, and 12.1%, respectively. At the 6-month follow-up, this rate had increased, but similarly for each cohort, i.e., 43.6%, 48.6%, and 44.9% for massed-PE, spaced-PE, and PCT, respectively.

Dr. Foa’s pioneering randomized clinical trial in active duty military personnel with combat-related PTSD demonstrated that spaced- and massed-PE reduce PTSD symptom severity to a similar degree. Massed-PE treatment may reduce Service members’ prolonged suffering from the negative consequences of combat-related PTSD. Additionally, Service members who are unable to participate in traditional spaced-PE because of their military duties could be referred to intensive in-patient treatment centers, receive massed-PE treatment, and expedite their return to duty.


Foa EB, McLean CP, Zang Y, et al. 2018. Effect of prolonged exposure therapy delivered over 2 weeks vs 8 weeks vs present-centered therapy on PTSD symptom severity in military personnel: A randomized clinical trial. JAMA 319(4):354-364.


Public and Technical Abstracts: The STRONG STAR Multidisciplinary PTSD Research Consortium

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Last updated Thursday, May 26, 2022