Internet-based cognitive-behavioural interventions seem to be effective for the treatment of posttraumatic stress disorder (PTSD) in Arabic-speaking countries in the MENA region. However, due to high prevalence rates of trauma-related mental disorders in this region, it is important to scale up existing Internet-based interventions in order to increase the number of clients. Objective The aim of the study was to examine whether a brief Internet-based intervention with one cognitive technique

more »

... -short, 6 assignments) results in the same PTSD symptom change and lower dropouts compared to a longer intervention with two cognitive techniques (TF-reg, 10 assignments). Method A total of 224 Arab participants (67.4% female; M = 25.3 years old) with PTSD were randomly assigned to Internet-based CBT with either a TF-reg protocol (n = 110) or a TF-short protocol (n = 114). Symptoms of PTSD and secondary outcomes (anxiety, depression, somatic complaints, quality of life) were self-assessed online at baseline and post-treatment. Treatment-associated changes were estimated using multigroup latent difference score models. Results The overall PTSD score assessed with the PDS decreased by about 15 points in both conditions. The between-group differences (TF-reg vs. TF-short) at post-assessment were non-significant, Δ = 0.29, p = .896, d = 0.02, 95% CI [-0.30, 0.34]. Like the primary outcome, all within-group changes for the secondary outcomes throughout the intervention were statistically significant and all between-group effects were non-significant. Overall, the dropout rates did not differ between the two conditions, χ2 (1/N = 175) = 0.83, p = .364. Conclusions The findings suggest that the shorter condition results in the same symptom change and dropout rate as the longer condition. This highlights the potential of shorter, more scalable Internet-based interventions in socially restricted and (post-)conflict societies.