The goal of this clinical trial is to test if Written Exposure Therapy (WET) works well in a group setting in patients with post-traumatic stress disorder (PTSD). The main questions it aims to answer are: * Does group WET lead to a reduction in symptoms of PTSD? * Is group WET better at reducing the number of patients that drop out of treatment in comparison to group Cognitive Processing Therapy (CPT)? Participants will: * Attend 6 weekly sessions of group WET that will be delivered online by two therapists (psychologist and social worker) * Complete questionnaires relating to their symptoms at different points throughout the treatment Researchers will evaluate change in PTSD symptoms over time for people who participate in group WET. They will also compare the results of group WET to the results of group CPT to see if group WET shows a similar reduction in symptoms of PTSD and fewer treatment drop-outs.