Credibility and expectations: Important factors for understanding clinical response, treatment completion, and dropout in internet-delivered psychological interventions.

OBJECTIVE: Several large studies have identified perceptions of treatment credibility and treatment outcome expectations as potential moderators of treatment response in internet-delivered psychological treatment. However, no studies have specifically focused on these two constructs and their potential roles in the moderation of treatment-related change, treatment completion, or study dropout.

METHOD: Adult samples were derived from four large randomized controlled trials examining internet-delivered treatment for symptoms of depression (n = 445), generalized anxiety (n = 454), social anxiety (n = 486), and panic disorder (n = 292). In these studies, relevant symptom measures were administered at pretreatment and posttreatment, and credibility and expectancy were assessed in Week 2 after participants had had some experience with treatment.

RESULTS: Treatment credibility and outcome expectations were relatively high overall, with a majority of participants scoring in the upper ranges. Both variables significantly moderated treatment response across all symptom domains. Specifically, each 1-point increase in either average credibility scores or average expectancy scores were associated with a 5%-8% reduction in symptoms at posttreatment. Higher treatment credibility and outcome expectations were also significantly associated with increased treatment completion and lower rates of study dropout or missingness.

CONCLUSIONS: The findings suggest that perceptions of treatment credibility and outcome expectancies are important factors in understanding treatment engagement and response to internet-delivered interventions. (PsycInfo Database Record (c) 2025 APA, all rights reserved).