Symposia
Trauma and Stressor Related Disorders and Disasters
Jenna M. Bagley, B.S., B.A.
Case Western Reserve University
Cleveland, Ohio
Norah Feeny, PhD
Professor
Case Western Reserve University
Cleveland, Ohio
Allison Baier, MA
doctoral Intern
Case Western Reserve University
Cleveland, Ohio
Alexandra Klein, MA
Graduate Student
Case Western Reserve University
Cleveland, Ohio
Lori Zoellner, PhD
Professor
University of Washington
Seattle, Washington
Background: Understanding adequate treatment dose is critical for optimizing effective selection and efficient delivery of psychological interventions (Cohen & DeRubeis, 2018). Prior research suggests 8 sessions of prolonged exposure (PE) therapy to be an adequate dose (e.g., Mott et al., 2014); however, session dosage for pharmacotherapies and combination treatments for PTSD is less understood. This study examined whether treatment type impacted symptom reduction and treatment response by Session 8.
Method: Patients with chronic PTSD (N = 350) received 10 weeks of PE only, sertraline only, or PE plus sertraline. PTSD symptoms were assessed on the PTSD Symptom Scale (PSS-SR; Foa et al., 1993) weekly across treatment sessions. A treatment response variable was created combining two indices of response from Sessions 1 to 8; endorsing either loss of diagnosis (falling below the clinical cutoff score of 20) or clinically meaningful symptom change (a reduction of at least 50%; Foa et al., 1993).
Results: Preliminary results suggest that, on average, patients experienced clinically significant change on the PSS-SR by Session 8 (M = -14.73; SD = 11.75, d = 1.44) with no observed differences by treatment condition, F(2, 313) = 2.04, p =.186, ηp2 = .013. By Session 8, the majority of patients achieved loss of diagnosis and/or clinically meaningful change (60.3%), with no differences between treatment groups (χ²(2, N = 319) = 1.47, p =.627). Exploratory post-hoc analyses investigated response rates at Sessions 6 and 10. Across treatments, loss of diagnosis and/or meaningful change attainment was 23.2% lower at Session 6 (χ²(2, N = 317) = 2.08; NNT = 7.1) than at Session 8 and increased from Session 8 to 10 by 25.9% (χ²(2, N = 319) = 1.09; NNT = 6.4).
Conclusions: Differences in improvement by Session 8 were not seen across treatment conditions, suggesting “adequate dose” may not differ substantively between PE, sertraline, and PE plus sertraline. Further, although the majority of patients made clinically meaningful improvement by Session 8, a substantial minority benefited from two additional sessions. Findings support previous work on psychotherapy dose (e.g., Mott et al., 2014) and expand the literature on adequate dose for differing PTSD interventions. Future work should investigate how these treatments may be similar in terms of adequate session dosage, despite having potentially different mechanisms, and identify individual predictors of session response to better inform treatment selection and delivery.