Within- and between-patients associations between self-efficacy, outcome expectation, and symptom change in cognitive behavioral therapy for generalized anxiety disorder.

Objectives: There is limited information on how a change in patients' expectations over time results in symptom change in psychotherapy. This study aimed to investigate the changes in patients' expectations and symptoms during treatment and across follow-up as well as to determine the within- and between-patient relationships between two types of patient expectations, that is, self-efficacy and outcome expectation, and symptom change.

Methods: Participants (80 participants × 6 repeated measures; 480 observations) with generalized anxiety disorder were treated using cognitive behavioral therapy and the within- and between-patient scores of self-efficacy and outcome expectation were evaluated in multilevel models as predictors of symptom change.

Results: Patients' self-efficacy and outcome expectation increased, whereas severity of their symptoms reduced during and after treatment. At the within-patient (WP) level, an increase in self-efficacy was associated with a decrease in worry and depressive symptoms, and an increase in outcome expectation was associated with a decrease in depressive symptoms. The between-patient (BP) effect, however, was contrary to the WP effect, that is, self-efficacy was positively correlated with worry and outcome expectation was positively correlated with depressive symptoms CONCLUSION: These results highlight the importance of disaggregating the WP variability from BP variability in psychotherapy process-outcome research as they exhibit different associations at the within- and between-patient levels. Clinical Trial Registration: ClinicalTrial.gov (NCT03079336).