Actor-partner outcome expectation-alliance associations in naturalistic psychotherapy

Meta-analyses indicate that patient outcome expectation (OE) and therapeutic alliance quality each correlate positively with improvement across diverse psychotherapies. Moreover, research demonstrates that these constructs relate to one another, including higher OE correlating with better subsequent alliance. However, notable gaps in this area remain. First, most studies that have examined the OE-alliance association have done so from the patient perspective only, despite both constructs having dyadic properties. Second, few studies have examined the connection between these two constructs longitudinally to capture their dynamic interrelations. Third, few studies have parsed OE-alliance links into their within- and between-dyad components, masking interpretability. Finally, most studies derive from controlled trials for specific diagnoses, limiting generalizability. Addressing these gaps, we tested the dyadic, dynamic, and statistically parsed associations among patient and therapist OE and alliance in naturalistic psychotherapy. Patients and therapists rated OE and alliance quality across up to 16 weeks of treatment. For dyads with the requisite data (N = 111 patients nested within 37 therapists), we used a multilevel actor-partner interdependence model that simultaneously tested all within- and between-dyad actor and partner effects of OE on alliance quality. At the within-dyad level, there were no significant actor or partner effects. At the between-dyad level, there were no significant partner effects, but there was a positive OE-alliance actor effect for both patients and therapists. Results suggest that community-based therapists may consider attending most to each participant's average level of OE across therapy (vs. fluctuations) when forecasting its influence on their own overall relationship experience. (PsycInfo Database Record (c) 2025 APA, all rights reserved).