(PS10-C65) Therapeutic Alliance as an Indirect Effect on the Association Between Treatment Credibility and Posttreatment Outcomes in a Novel Positive Processing-focused Treatment (PATH) for PTSD and Depression

Introduction: Treatment credibility has been associated with improved psychotherapy outcomes, including for posttraumatic stress disorder (PTSD) and major depressive disorder (MDD; Constantino et al. 2018). A strong therapeutic alliance might explain this relationship.  Positive Processes and Transition to Health (PATH) is a novel transdiagnostic intervention that focuses on building adaptive processes following destabilizing life events (e.g., sexual assault, job loss), promoting constructive processing, approach, and positive engagement. This study investigated whether therapeutic alliance had an indirect effect on the relationships between early perceptions of treatment credibility and post-treatment PTSD and depression symptoms following PATH.

Method: We analyzed data from the ongoing, open trial of PATH (NCT04678232; n = 19; target N = 45) for participants with elevated PTSD and/or depressive symptoms following a destabilizing life event. We conducted our analyses with a subsample, yet final results will be reported after study completion. Participants self-reported their perceived treatment credibility after session 1 via the Personal Reactions to the Rationales and Credibility Scale (PRR + CS; Addis & Carpenter, 1999). Therapeutic alliance was measured using the Working Alliance Questionnaire (WAQ; Falkenström, 2015) after each session. Self-reported symptoms of PTSD and depression were collected at baseline and at post-treatment using the Posttraumatic Diagnostic Scale-5 (PDS-5; Foa et al., 2015) and Quick Inventory of Depressive Symptomology (QIDS-SR; Rush et al., 2003). Regression analyses (Hayes’ PROCESS Model 4) were conducted to examine alliance (average of sessions 1 – 6) as a potential mediator of the relationship between perceived treatment credibility and PTSD and depression symptom outcomes.

Results: Controlling for baseline symptoms, credibility ratings predicted therapeutic alliance in both models (PTSD: β = 0.73, p = .05; depression: β = 0.76, p = .05), but neither credibility ratings (PTSD: β = 1.72, p = .17; depression; β = 0.54, p = .12) nor alliance (PTSD: β = -1.50, p = .15; depression: β = -0.13, p = .61) predicted outcomes at post-treatment. Therefore, alliance was not examined as an indirect effect between credibility and PTSD or depression outcomes. Conclusion: Extending previous findings to this novel intervention, higher treatment credibility was associated with better therapeutic alliance (Fjermestad et al., 2018), and there was no indirect effect of alliance on the relationship between credibility and outcome (Söchting et al. 2016). Contrary to previous findings, alliance did not predict post-treatment outcomes, potentially due to ceiling effects and low variability of the alliance measure (M = 27.5, SD = 3.96, max = 30). Future research should investigate factors that may mediate the relationship between perceived treatment credibility and posttreatment outcomes, such as the role of specific therapist behaviors or client characteristics.