Through Agency or Alliance? A Multilevel Mediation Study on the Indirect Effects of Outcome Expectations on Symptom Improvement

This study investigated the impact of client outcome expectations on symptom improvement and evaluated the underlying mediating roles of therapeutic agency and working alliance. Data were collected from 73 clients across 12 sessions and analyzed using a multilevel lagged mediation framework. Outcome expectations significantly predicted subsequent symptom reduction at both the between‐person and within‐person levels, functioning as both trait‐like and state‐like factors. Therapeutic agency emerged as a significant mediator at both levels: clients with higher average expectations exhibited greater agency, which was associated with improved symptoms (between‐person effect), and session‐to‐session increases in expectations predicted enhanced next‐session agency, which in turn predicted symptom reduction (within‐person effect). Working alliance did not demonstrate a significant mediating effect at either level. Within this sample, these findings point to the potential value of monitoring session‐to‐session fluctuations in outcome expectations and implementing targeted interventions to facilitate their translation into therapeutic agency.