Trials of exposure-based CBTs conducted in the last several years generally included components of psychoeducation, breathing, and relaxation training. By definition, these exposure therapies also incorporated into the therapy sessions some form of reexposure to past traumatic experience (e.g., imaginal, in vivo, directed therapeutic, written, verbal, or taped narrative recountings). In addition, homework was often included. The generalizability of the results of many of these studies to typical clinical populations is limited by high dropout rates, lack of intention-to-treat analysis, and lack of clarity regarding blinding of assessors. Nevertheless, several well-designed studies augment prior knowledge.

In 2006, Monson et al. (38) reported the results of a waitlist-controlled study of cognitive processing therapy in 60 combat veterans. The overall dropout rate was 16.6% (20% from cognitive processing therapy, 13% from waitlist), but random regression analyses of the intention-to-treat sample revealed significant improvements in both PTSD and co-occurring depressive symptoms in the treatment group compared with the waitlist group. At completion of the study, 40% of those in the intention-to-treat group receiving cognitive processing therapy no longer met criteria for a PTSD diagnosis, and 50% had a reliable decrease in their PTSD symptoms.

The effectiveness of cognitive processing therapy was also examined in a controlled study reported in 2005 by Chard (39) of 71 adult sexual abuse survivors with PTSD. The control was a minimal-attention waitlist group. Participants were assessed pretreatment, immediately after treatment, 3 months after treatment, and 1 year after treatment using the CAPS and a variety of other clinician-administered rating scales. Analysis demonstrated that cognitive processing therapy was superior to waitlist in reducing PTSD symptoms and that reductions were maintained for at least 1 year.

A recent study by Resick et al. (40) attempted to dismantle the components of cognitive processing therapy and determine their relative contributions to treatment efficacy. In this study, 150 adult women with PTSD were randomized into one of three conditions: 1) full cognitive processing therapy, which included both exposure (i.e., writing and reading a detailed account of the trauma) and cognitive therapy (i.e., challenging patient assertions about the meaning of the trauma and the implications for the patient's life); 2) cognitive therapy without the writing and reading component; and 3) the writing and reading component without cognitive therapy. All conditions included 2 hours of therapy per week for 6 weeks. Patients were assessed for PTSD (using CAPS) and depression in a blinded manner weekly, 2 weeks after the last session of therapy, and at 6 months. At the conclusion of the study, all treatment completers still met criteria for PTSD. However, substantial improvement was observed in all three treatment groups on primary PTSD and depression outcomes as well as on secondary measures of anxiety, guilt, and shame. Cognitive therapy without exposure was associated with greater improvement than the exposure-only condition, suggesting that the cognitive component of this therapy (i.e., altering the meaning of the traumatic event) may be an active treatment mechanism that may occur without repeated and explicitly evoked fear memories. It also suggests that cognitive processing therapy might be characterized as a more cognitive than exposure-based therapy. Similar dismantling studies are under way and will be important to further clarify the active components of various psychotherapies for PTSD. Research questions include how cognitive components as compared with exposure components may be variably effective depending on factors such as the stage of the disorder (e.g., early compared with late), the presence of particular symptoms (e.g., dissociation, high levels of arousal, avoidance), and, of course, therapist variables.

Prolonged exposure therapy was studied in a randomized controlled trial reported in 2007 by Schnurr et al. (41) of female veterans (N = 277) and active duty personnel (N = 7) across 12 sites specializing in medical treatment for military veterans, including nine Veterans Affairs hospitals, two Veterans Affairs counseling centers, and one military hospital. Patients were randomly assigned to receive prolonged exposure therapy (N = 141) or present-centered therapy (N = 143) delivered in 10 weekly 90-minute sessions. Blinded assessors collected data before and immediately after treatment and 3 and 6 months after treatment. Immediately after treatment, the prolonged exposure group was more likely than the present-centered therapy group to no longer meet PTSD criteria (41% compared with 27.8%, odds ratio [OR] = 1.80, confidence interval [CI] = 95%) and more likely to achieve full remission (15.2% compared with 6.9%, OR = 2.43, CI = 95%). These results were maintained at 3- and 6-month follow-up. It should be noted that although this was a study of military personnel and veterans, 70% of participants indicated sexual trauma as their index (worst) traumatic experience, and there was a 17% differential dropout rate between prolonged exposure and present-centered therapy, with more participants dropping out of the prolonged exposure arm.

A controlled study reported in 2005 by Rothbaum et al. (42) evaluated the relative efficacy of prolonged exposure therapy and EMDR. In this study, 74 adult female rape victims (index rape occurring either in adulthood or childhood) were randomized into 9-session prolonged exposure, EMDR, and waitlist control groups. Dropout rates across the groups were not significantly different (13% prolonged exposure, 20% EMDR, 16.7% waitlist). Immediately following treatment, the groups receiving prolonged exposure and EMDR both demonstrated statistically significant improvement across three outcome measures, including a 50% or more decrease from baseline in CAPS score (p = 0.001). Posttreatment, 95% of participants who received prolonged exposure therapy and 75% of participants who received EMDR no longer met criteria for PTSD, and individuals who received both treatments showed significantly reduced depressive symptoms and dissociative symptoms immediately and at 6 months. Results were maintained at 6-month follow-up for the prolonged-exposure group across PTSD, depressive, and dissociative symptoms but maintained to a significantly lesser extent for the EMDR group with regard to PTSD.

The effectiveness of brief exposure therapy has been demonstrated in two recent studies reported in 2005 and 2007 by Basoglu et al. (43, 44). In the first study, 59 earthquake survivors with PTSD assessed by CAPS were randomized to a single-session exposure-based behavioral therapy intervention (in which the intensity of simulated trauma was adjusted in accordance with the patient's personal feelings of comfort) or to a waitlist (43). At 6, 12, and 24 weeks posttreatment, as well as at 1–2 years posttreatment, the treatment group was observed to have significant decreases in CAPS score, Beck Depression Inventory (BDI) score, and other patient self-measures of fear, anxiety, or overall impression. With regard to CAPS, effect sizes were considerable (Cohen's d = 0.7–1.4), and improvement rate rose from 49% at week 6 to over 80% at other assessment points.

In the second study (44), 31 earthquake survivors with PTSD were randomized to a single-session exposure-based behavioral therapy (N = 16) or to repeated assessments (N = 15). Participants were assessed at 4, 8, 12, and 24 weeks posttreatment and again after 1–2 years. Again, significant between-group treatment effects were observed in PTSD (assessed by CAPS) and assessor-rated global improvement (Global Improvement Scale–Assessor [GIS–A]), with significant between-group treatment effects observed in both outcome measures at week 8. Improvement rates of 40% at week 4 rose to 80% by week 24 and at 1–2 year follow-up, with large effect sizes (Cohen's d = 0.9–1.7) noted across primary measures at week 8.