Examining why therapists add sessions to the written exposure therapy protocol and whether it improves treatment outcome: A mixed-methods analysis.

Written exposure therapy (WET) is a brief psychotherapy for posttraumatic stress disorder (PTSD). Although WET is designed to be delivered in five sessions, implementation data collected from trained mental health care providers suggest that therapists sometimes add more sessions without sufficient justification. We conducted a mixed-methods examination to understand why therapists added WET sessions and whether adding sessions improved treatment outcomes. Participants were drawn from a larger trial where therapists were permitted to deliver five to seven WET sessions. This study included 77 client participants who were randomly assigned to receive WET and nine therapist participants who delivered WET during the trial. Results showed that PTSD symptom severity trajectories at follow-up assessment were not significantly different between client participants who received five sessions and those who received more than five. Only 15.7% of participants who received supplemental WET sessions displayed a clinically meaningful reduction in PTSD symptom severity, while 11.8% displayed a clinically meaningful increase in PTSD symptom severity. Qualitative interviews with therapists indicated that their decision to add sessions was largely driven by the client avoiding writing about the traumatic event in early treatment sessions or due to a very complex or lengthy traumatic event that required additional sessions to provide repeated exposure to the trauma memory. Taken together, the findings suggest that adding WET sessions is unnecessary most of the time, but therapists have a strong preference for having flexibility in adding treatment sessions. (PsycInfo Database Record (c) 2026 APA, all rights reserved).