The present study aimed to investigate the efficacy of 60-minute sessions of prolonged exposure (PE) for patients with posttraumatic stress disorder (PTSD) in Taiwan. A systematic case study will be employed to compare the efficacy of 60-minute PE session versus standard 90-minute session with eight Taiwanese PTSD patients. Participants will include the individuals aged 18 or older who meet a diagnosis of DSM-5 PTSD and to experience moderate to severe symptoms for at least 3 months. Those who have current substance dependence, psychosis, and acute suicidality (i.e., recent suicidal ideation with intent and plan) will be excluded. Participants will receive 10-15 weekly session of PE treatment with 60- or 90-minute sessions. The investigators hypothesized that: (a) 60-minute PE is as effective as 90-minute PE in reducing PTSD and depressive symptoms as well as in promoting posttraumatic growth (PTG); and (b) the treatment gains will be maintained at 3-month follow-up.

Background: Posttraumatic stress disorder (PTSD) is a common psychological disorder following trauma and disaster. Due to the frequent occurrence of disasters induced by natural hazards, many Taiwanese people suffer from post-disaster mental health problems, suggesting the necessity of promoting evidence-based psychotherapies for PTSD in Taiwan. However, there has been little concern about this necessity over the past decades. To date, several evidence-based psychotherapies for PTSD have been developed, and prolonged exposure treatment (PE) has the largest number of studies supporting its efficacy and effectiveness. PE has been found effective with the widest range of trauma populations and has been studies across cultures. Given its strong evidence base, the investigators tested the efficacy and feasibility of PE for Taiwanese PTSD patients. It is noted that the original length of PE session is 90 minutes, which is difficult to get reimbursement by insurance and may prevent mental health professionals to use PE. Recent researchers shortened the length of PE session to 60 minutes and found its efficacy was non-inferior to standard 90-minute PE session (Nacasch et al., 2015; van Minnen & Foa, 2006). Accordingly, this study aims to examine the efficacy of 60-minute PE sessions versus standard 90-minute session for patients with PTSD in Taiwan.

Study Hypothesis: (a) 60-minute PE session is as effective as 90-minute PE session in reducing PTSD and depressive symptoms as well as in promoting posttraumatic growth (PTG); and (b) the treatment gains will be maintained at 3-month follow-up. A systematic case study will be employed to test the hypotheses.

Participants: Participants will include eight individuals aged 18 or older who meet a diagnosis of DSM-5 PTSD and to experience moderate to severe symptoms for at least 3 months. Those who have current substance dependence, psychosis, and acute suicidality (i.e., recent suicidal ideation with intent and plan) will be excluded.

Study Design: All enrolled participants will attend 10-15 weekly 60- or 90-minute PE sessions. Independent evaluators will assess PTSD diagnosis using the PTSD Symptoms Scale Interview for DSM-5 (PSSI-5) at pre- and post-treatment and at the three-month follow-up. Psychiatric comorbidity will be assessed using the MINI 7.0.2 at pretreatment. Participants will complete the Posttraumatic Diagnostic Scale for DSM-5 (PDS-5), Beck Depression Inventory-II (BDI-II), Beck Anxiety Inventory (BAI), Posttraumatic Cognitions Inventory (PTCI), and Posttraumatic Growth Inventory -Extended version (PTGI-X) at pre- and post-treatment and at the three-month follow-up. The PDS-5 and BDI-II will also be administered every two weeks during treatment.

Statistical Analysis: The nonparametric tests will be used given the small sample size. Wilcoxon signed-rank test will be conducted to test pre-post differences. Mann-Whitney U test will be conducted examine whether 60-minute PE session is as effective as 90-minute PE session in reducing PTSD and depressive symptoms as well as increasing PTG at post-treatment and three-month follow-up.

Expected Outcome: The investigators except that shortened PE will result in substantial improvement in PTSD and depressive symptoms in patients with PTSD in Taiwan.

Inclusion Criteria:

• primary diagnosis of DSM-5 PTSD, with moderate to severe symptoms for at least 3 months

Exclusion Criteria:

• organic mental disorder, current substance dependence, psychosis, acute suicidality (i.e., suicidal ideation with intent and plan), and severe dissociation.