Post-traumatic stress disorder (PTSD) is a highly distressing and debilitating disorder [1]. Numerous studies on the effects of PTSD have consistently shown various disabilities in functional aspects, such as occupational impairment [2], unemployment and low income [3,4], interpersonal problems [5,6], and high psychiatric [7] and medical comorbidities [8]. Thus, chronic PTSD represents a significant public health problem.

To address this public health threat, some evidence-based treatments (EBT) for PTSD have been developed, and their effectiveness has been demonstrated. These include trauma-focused cognitive behavioral therapy, cognitive processing therapy (CPT), and prolonged exposure therapy (PE). These are strongly recommended first-line therapies in major PTSD treatment guidelines [9].

Recently, Sloan and Marx’s [10] research team introduced a five-session exposure-based PTSD treatment protocol called written exposure therapy (WET). WET is recommended for the treatment of PTSD in clinical practice guidelines (Department of Veterans Affairs/Department of Defense, 2017). Like other EBTs, it comprises critical components considered to be responsible for the successful treatment of PTSD symptoms, such as therapeutic exposure and cognitive processing/cognitive restructuring [10-12]. However, WET requires a smaller number of sessions, shorter session durations, and no between-session assignments [10,13].

The efficacy of WET was evaluated using a randomized controlled trial, and this study reported a significant reduction in PTSD symptom severity at the post-treatment follow-up, and symptom reduction was maintained three and six months later with 7% of drop-out rate [14]. A study that directly compared WET to CPT indicated that WET was non-inferior to CPT [15]. Additionally, WET resulted in substantially lower rates of treatment dropout compared to CPT (6% vs. 39%) [15]. The effects of treatment were also long-term, specifically lasting for 60 weeks [16,17].

In order to apply WET to Korean patients, we must consider their different cultural background, which is dissimilar to Westerners. According to a study conducted in Japan, which is culturally similar to Korea, only 15% of respondents choose to disclose their trauma [18]. This tendency to be reluctant to express and verbalize trauma might be a barrier to exposure therapy. However, PE identical to the original version yielded the same effectiveness as western studies in Japanese studies [19,20]. Furthermore, Korean culture has been influenced by Western cultures in some way, such that they share a few basic assumptions [21]. These common aspects are expected to help in successfully applying WET to Korean patients without a need to modify the protocols. Therefore, further evidence is needed regarding the applicability of WET to different population groups.

We aimed to address this issue by implementing WET on Korean patients with PTSD. Subsequently, we compared the participants’ PTSD symptoms, depressive symptoms, and global functioning levels before and after treatment.

A total of 43 patients were screened for PTSD using the SCID; of which, 41 participants were diagnosed with PTSD (Figure 1). One person was excluded because of seizure-like conversion symptoms, which was deemed unsuitable for exposure therapy. Six individuals were eligible but did not attend the baseline assessment. Thirty-four participants completed the baseline assessment. Table 1 shows the 34 participants’ sociodemographic and clinical characteristics.

Of the 34 patients with PTSD who completed the baseline assessment, 14 (44.1%) had a diagnosis of comorbid depression. The median PTSD duration was 14 months. Nine of the 34 participants dropped out spontaneously before commencing treatment. Ultimately, 25 people started WET. Five of the 25 participants had PTSD for less than 12 months. Among those who dropped out (n=9), duration of PTSD was significantly shorter (14.56±27.14 vs. 43.72±41.15, t=-2.385, p=0.026) than participants who started WET. Socio-demographic factors and demographic factors did not differ significantly between the two groups.

Two of the 25 participants who started WET discontinued treatment at the first and second sessions, respectively. Both were women who had been sexually assaulted, one in childhood and one in adulthood. The remaining 23 participants completed five therapy sessions, as well as the 6- (23 of 23), 12- (22 of 23), and 24-weeks (18 of 22) follow-up assessments. No severe adverse events were observed during the study.

Table 2 shows significant reductions in CAPS, PCL-5, and PHQ-9 scores after the treatment (6 weeks follow-up; T2), 12 weeks (T3), and 24 weeks (T4) follow-up. The GAF score also significantly increased after the treatment (T2, T3, and T4). At 6 weeks (T2), 14 of 23 (60.9%) participants no longer met the PTSD diagnosis. Of the 23 participants, one did not complete the 12 weeks follow-up assessment. Among them, 15 (68.2%) participants no longer met the PTSD diagnosis. Compared to the 6 weeks assessment, four additional participants did not meet the PTSD diagnosis at 12 weeks. Meanwhile, two participants who had shown improvements at 6 weeks were diagnosed with PTSD again at 12 weeks. At 24 weeks, four participants missed the follow-up assessment. Two of them had no PTSD diagnosis at the 12 weeks follow-up, and the other two showed no improvement at 12 weeks. At 24 weeks, 14 participants (77.8%) no longer met the PTSD diagnosis.

All scores were significantly reduced at each follow-up assessment compared to those at baseline (Table 2). The rmANOVA results indicated that the scores of CAPS (F 40.278, p<0.001), GAF (F 22.989, p<0.001), PCL-5 (F 17.611, p<0.001), and PHQ-9 (F 18.530, p<0.001) significantly reduced over time (Figure 2) and yielded large effect size (CAPS 0.703, PCL-5 0.524, PHQ9 0.537, GAF 0.575).

There were no significant differences between participants who did not satisfy the PTSD diagnosis and those who did according to demographic and clinical characteristics, except for baseline symptom scores. There was no difference in PTSD duration between the two groups (improved:non-improved group (mean±SD); at 6-week 35.36±39.16:52.67±42.00, p=0.439, at 12-week 43.53±40.55:43.43±44.19, p=0.891, at 24-week 41.63±11.13:45.25±45.06, p=0.959). There were significant differences in the PCL-5, PHQ-9, and CAPS scores at baseline between the two groups in the 6 weeks follow-up assessment (Table 3). There was a significant difference in the diagnosis of comorbid depression at baseline between the two groups in the follow-up assessments at 6 and 12 weeks. At the 12 weeks follow-up assessment, the participants who did not meet the PTSD diagnosis had higher satisfaction after treatment than those who still met the PTSD diagnosis. However, these differences were not statistically significant at 24 weeks.

This study aimed to explore the efficacy of WET among a Korean sample presenting with clinically diagnosed PTSD. Our findings demonstrate that Korean participants with PTSD benefitted significantly from a brief written exposure treatment. Specifically, self-reported and clinician-assessed PTSD symptoms, depressive symptoms, and overall functioning improved after participants underwent WET.

Numerous studies have demonstrated reductions in PTSD and related psychopathologies with exposure therapy [15,16,20,33]. However, global functioning is another measure of symptom reduction. Improvements in PTSD with exposure therapy were associated with improvements in psychosocial functioning [34,35]. Therefore, the reduction of PTSD symptoms through WET was expected to improve general functioning. Previous research has not reported on the improvement of functioning through WET; therefore, it is significant that the improvement of general functioning after WET was identified in this study.

We found that the treatment effect of WET was maintained at week 24. At the 12 and 24 week follow-up, 4 and 2 additional participants respectively showed improvements in PTSD. Several theories explain the mechanisms for the effects of WET. Traditionally, the emotional processing theory [36] and cognitive models of PTSD [37] underpin EBT, such as PE and CPT. Thus, WET may reduce PTSD and other symptoms through habituation during five sessions; specifically, by helping individuals more effectively organize and integrate their traumatic memories [14]. Inhibitory learning, a recently supported mechanism for exposure therapy, may also be an important mechanism for this treatment effect and maintaining the effects of WET. Inhibitory learning through EBT, including WET, provide the opportunity to be instilled with a sense of unconditional learned safety [38]. It is expected that patients will continue to utilize concepts learned from exposure therapy in daily life after the end of formal therapy sessions [38].

We analyzed the difference between the two groups according to treatment outcome at each follow up assessment. Sociodemographic factors, trauma-related variables such as age at the time of trauma exposure, and trauma type were not different between two groups. These results are similar to those of previous studies. Although benzodiazepine use is associated with more symptoms at follow-up after PE [13,17,39], our findings did not show an association between benzodiazepine use and treatment outcome.

The results of this study demonstrate that WET was well-tolerated and well-received by Korean participants. The dropout rates during WET in Western studies was around 6%-9% [14,15]. Similarly, the dropout rate in this study was 8%. However, it is evidently lower compared to the 24% to 36% drop-out rates reported in previous PE or CPT studies [40,41].

Despite recent treatment guidelines for PTSD, which recommend exposure therapy as a first-line treatment, the issues of Korean mental health care services, including low medical fees for psychotherapy, quantity-oriented hospital evaluations, and heavy outpatient workload [42] are barrier to conduct EBTs for PTSD in Korea. Thus, we suggest that the brevity and tolerability of WET is an efficient and effective alternative therapy in the Korean medical system.

This study is meaningful as it is the first Asian study performed and evaluated by certified professions to prove the effects of WET. In addition, in this study, WET was implemented for patients with clinically diagnosed PTSD, and the effectiveness of treatment was evaluated by clinical evaluators. However, there are several limitations to our study. First, our experiment was an uncontrolled trial and we only analyzed completer data. Therefore, our findings, though significant, could not be considered conclusive. Second, suicidal patients with present suicidal ideation severe enough to warrant immediate intervention were excluded from the present study. Therefore, it should be noted that these conclusions should not be generalized to PTSD patients that present suicidal intent. Third, all sessions were served by only one therapist. It is reported that the therapist effects in naturalistic studies averaged 5% [43], and the effects of therapist effect cannot be completely excluded in this study. Fourth, medication effect might contribute to the significant reduction of symptoms after WET in this study. To minimize the effect of pharmacotherapy, all participants maintained the dose of medication at least 8 weeks before the first session. During the 5 sessions, medication dose was maintained. In addition, no subjects increased their medication dose in the follow-up period. Finally, the follow-up period was not enough long, therefore the long-term treatment effects of WET could not be confirmed in this study. In the future, long-term follow-up research on Asian samples is needed to obtain conclusive results.

In conclusion, this study suggests the feasibility of implementing WET for various types of patients with PTSD in Korea and other Asian countries. This will improve not only PTSD symptoms, but also depressive symptoms and general functioning. Future large-scale randomized controlled trials investigating the effectiveness of WET in the Asian population are necessary.