Supplementary Material for: An Online Guided Written Exposure Therapy for Symptoms of Posttraumatic Stress Disorder: A Randomized Controlled Trial

Introduction: Access to effective post-traumatic stress disorder (PTSD) treatment is limited in low-resource regions (LRRs). Methods: We conducted a randomized controlled trial to evaluate the efficacy of Guided Written Exposure (GWE), an online therapy developed for LRRs, in reducing PTSD, depression, and insomnia symptoms compared to minimal contact control (MCC). Adults (N=95) meeting DSM-5 criteria for PTSD or subthreshold PTSD were randomly assigned to GWE (N=65) or MCC (N=30) in China from June 27, 2022, to August 11, 2023, with a final follow-up on April 16, 2024. Assessments were conducted at pre-treatment, post-treatment, and 1-month follow-up for both groups, and at 3- and 6-month follow-ups for the GWE group. The primary outcome was the PTSD Symptom Scale Interview-DSM5 (PSSI-5, assessed by blinded evaluators) and PTSD CheckList-5 (PCL-5).Results: GWE had significantly lower PSSI-5 (1-month: d=-0·74, 95% CI [-0·98, -0·51], p<·001) and lower PCL-5 (1-month: d=-0·79, 95% CI [-1·03, -0·54], p<·001) than MCC. Reliable change in PTSD symptoms at 1-month: GWE 65% (42/65) vs. MCC 37% (11/30), p=·01. GWE also had significantly lower depression and insomnia severity than MCC at post-treatment and 1-month follow-up. Effects maintained through 6 months for PTSD, depression, and insomnia in the GWE group. Conclusions: GWE may be an efficacious intervention for individuals with PTSD in LRRs.