Psychotherapy for PTSD - a scoping review of how change during treatment has been studied

Background: Posttraumatic Stress Disorder (PTSD) treatment shows 40% of non-response rate despite the efficacy of evidence-based psychotherapies like Prolonged Exposure (PE), and Cognitive Processing Therapy (CPT). Understanding how PTSD symptoms change during treatment, and the mechanisms that precede, mediate, or moderate these changes, is essential for improving interventions.Objective: This systematic scoping review mapped how changes in PTSD have been studied during psychotherapy between 2000 and 2023, focusing on (1) research objectives, (2) PTSD conceptualization, (3) covariates and mechanisms included, (4) repeated measurement timing and frequency, and (5) statistical modelling of change.Methods: Following PRISMA guidelines, we searched scientific databases for English- and Spanish-language peer-reviewed studies. Eligible studies included adults diagnosed with PTSD, examined evidence-based psychotherapies, and incorporated at least three repeated in-treatment assessments. Excluded were pharmacological trials, case studies, and non-empirical articles. After a three-phase screening, 115 studies met inclusion criteria. Data were extracted on research objectives, measurements, demographics, and analytic methods, and summarized using descriptive statistics.Results: Most studies were conducted in the United States (82%) involving veterans or active military (50%). PE (50%) and CPT (31%) dominated the treatment landscape. A total of 207 research objectives were identified, grouped into 16 categories. The most frequent were temporal precedence, time-stable predictors, and identification of change trajectories. PTSD and depression were the most frequently measured constructs (83%), typically assessed session-by-session with an average of nine repeated measurements, aligned with protocol duration. Multilevel regression modelling was the predominant analytic strategy (48%).Conclusions: Future research should state causal aims openly and base measurement on theory and evidence rather than tradition. Exploratory studies are needed to build an accurate understanding of the timing of PTSD change. Crucially, no studies used ecological momentary assessment, and samples show limited generalizability. Finally, research efforts significantly increased since 2010, evidencing the importance of this type of research.