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

Abstract

Importance: Effective and efficient treatment is needed for posttraumatic stress disorder (PTSD) in active duty military personnel.

Objective: To examine the effects of massed prolonged exposure therapy (massed therapy), spaced prolonged exposure therapy (spaced therapy), present-centered therapy (PCT), and a minimal-contact control (MCC) on PTSD severity.

Design, setting, and participants: Randomized clinical trial conducted at Fort Hood, Texas, from January 2011 through July 2016 and enrolling 370 military personnel with PTSD who had returned from Iraq, Afghanistan, or both. Final follow-up was July 11, 2016.

Interventions: Prolonged exposure therapy, cognitive behavioral therapy involving exposure to trauma memories/reminders, administered as massed therapy (n = 110; 10 sessions over 2 weeks) or spaced therapy (n = 109; 10 sessions over 8 weeks); PCT, a non-trauma-focused therapy involving identifying/discussing daily stressors (n = 107; 10 sessions over 8 weeks); or MCC, telephone calls from therapists (n = 40; once weekly for 4 weeks).

Main outcomes and measures: Outcomes were assessed before and after treatment and at 2-week, 12-week, and 6-month follow-up. Primary outcome was interviewer-assessed PTSD symptom severity, measured by the PTSD Symptom Scale-Interview (PSS-I; range, 0-51; higher scores indicate greater PTSD severity; MCID, 3.18), used to assess efficacy of massed therapy at 2 weeks posttreatment vs MCC at week 4; noninferiority of massed therapy vs spaced therapy at 2 weeks and 12 weeks posttreatment (noninferiority margin, 50% [2.3 points on PSS-I, with 1-sided α = .05]); and efficacy of spaced therapy vs PCT at posttreatment.

Results: Among 370 randomized participants, data were analyzed for 366 (mean age, 32.7 [SD, 7.3] years; 44 women [12.0%]; mean baseline PSS-I score, 25.49 [6.36]), and 216 (59.0%) completed the study. At 2 weeks posttreatment, mean PSS-I score was 17.62 (mean decrease from baseline, 7.13) for massed therapy and 21.41 (mean decrease, 3.43) for MCC (difference in decrease, 3.70 [95% CI,0.72 to 6.68]; P = .02). At 2 weeks posttreatment, mean PSS-I score was 18.03 for spaced therapy (decrease, 7.29; difference in means vs massed therapy, 0.79 [1-sided 95% CI, -∞ to 2.29; P = .049 for noninferiority]) and at 12 weeks posttreatment was 18.88 for massed therapy (decrease, 6.32) and 18.34 for spaced therapy (decrease, 6.97; difference, 0.55 [1-sided 95% CI, -∞ to 2.05; P = .03 for noninferiority]). At posttreatment, PSS-I scores for PCT were 18.65 (decrease, 7.31; difference in decrease vs spaced therapy, 0.10 [95% CI, -2.48 to 2.27]; P = .93).

Conclusions and relevance: Among active duty military personnel with PTSD, massed therapy (10 sessions over 2 weeks) reduced PTSD symptom severity more than MCC at 2-week follow-up and was noninferior to spaced therapy (10 sessions over 8 weeks), and there was no significant difference between spaced therapy and PCT. The reductions in PTSD symptom severity with all treatments were relatively modest, suggesting that further research is needed to determine the clinical importance of these findings.

Trial registration: clinicaltrials.gov Identifier: NCT01049516.

Figure 1.. Flow of Participants Through the Study

PCL-S indicates PTSD Checklist–Stressor-Specific; PCT, present-centered therapy; PE, prolonged exposure therapy; UCMJ, Uniform Code of Military Justice. ^aA formal evaluation to determine whether a medical condition will impede a service member’s ability to continue serving in full duty capacity in his or her office, grade, or rank.

Figure 2.. Estimated Mean Scores for the Primary Outcome Measure (PSS-I) at All Time Points

Piecewise models with separate slopes during treatment and follow-up were used for mixed-model analyses of Posttraumatic Stress Scale–Interview (PSS-I) scores, and the following variables were included as covariates: baseline PSS-I, age, sex, and baseline mental and physical functioning. Final models were recomputed by dropping nonsignificant covariates in each analysis. Data are from the mixed-model analyses (MLM). Because different pairs of groups were included in the analysis for different hypotheses, MLM calculated different covariances between groups and time points, resulting in slightly different estimated mean scores for the spaced prolonged exposure therapy (spaced therapy) group depending on the hypothesis (2 or 3) being tested. This did not occur for present-centered therapy (PCT) or minimal-contact control (MCC), since they were only involved in 1 comparison each. For massed prolonged exposure therapy (massed therapy), the means for comparison to MCC were calculated from a subsample of 75 of the total n=110 because those 75 were recruited concurrently with the sample for MCC. The massed therapy means for comparing massed therapy with spaced therapy were from the entire sample of n=110 for massed therapy. The full range of scores on the PSS-I is 0-51. Error bars indicate 95% CIs from the mixed-model analyses. ^aThe elapsed time between baseline and end of treatment was 2 weeks for massed therapy and MCC and 8 weeks for spaced therapy and PCT.

Figure 3.. Difference Between Massed and Spaced Prolonged Exposure Therapy on Primary Outcome Measure (PSS-I) at 2-Week and 12-Week Follow-up

Range of possible scores on the Posttraumatic Stress Scale–Interview (PSS-I), 0 to 51. Boxes indicate the mean difference between massed prolonged exposure therapy (massed therapy) and spaced prolonged exposure therapy (spaced therapy); error bars indicate the 1-sided 95% CIs around the means. For massed therapy to be noninferior to spaced therapy, the upper bound of the 1-sided 95% CI for the difference between treatments (massed therapy minus spaced therapy) must be less than the noninferiority margin (2.3, blue dotted line).