Conducting behavioural experiments using an app-based self-help program for social anxiety disorder (SMASH): Outcomes of a quasi-experimental pre-post pilot trial [Author Accepted Manuscript]

Background. Social anxiety disorder (SAD) is a prevalent mental disorder characterised by fear of negative evaluation. Although effective treatment approaches are available, access remains limited due to psychological and organisational barriers. Internet-based cognitive behavioural therapy (iCBT) has shown promising results and may facilitate an easy and more resource-efficient access to treatment. Methods. We developed an app-based self-help intervention for SAD based on the Clark and Wells treatment program, implemented as an unguided smartphone application, which was evaluated in this quasi-experimental pre-post pilot study consisting of N = 33 patients with a primary diagnosis of SAD. Feasibility was assessed through usage parameters and qualitative feedback. Effectiveness was evaluated in regard to SAD and depression, using clinician-rated measures (LSAS, QIDS-C) at post-treatment (12 weeks) and self-report measures (SPIN, SCQ, BDI-FS) at midpoint and post-treatment. Additionally, moderating effects of usage parameters on symptom reduction were examined. Results. Clinician- and self-reported SAD symptoms were significantly reduced at post-measurement (within-group effect sizes LSAS: η^2 = .54; SPIN: η^2 = .47), with 52% of patients achieving a clinically significant improvement. Despite moderate overall adherence, the amount of conducted behavioural experiments moderated reduction in self-reported SAD symptom severity and SAD-related cognitions. Open feedback supported feasibility and acceptability of the app. Conclusion. In conclusion, findings provide preliminary support for feasibility, acceptability, and potential effectiveness of Mindable: Soziale Phobie. A randomised controlled trial will further evaluate the effectiveness and explore the impact of therapist guidance.