A Large-Group 1-Day RCT Investigating the Effectiveness of Four Different Strategies to Promote the Outcome of Exposure Therapy in 519 Patients with Phobic Fear of Flying

Introduction: Despite its status as the gold standard for treating fear and anxiety, exposure therapy leaves room for optimization. Clarifying and testing the clinical relevance of proposed mechanisms may enhance outcomes. This randomized controlled trial (DRKS00031220) examined the effects of four psychological strategies aimed at facilitating exposure outcomes in individuals with clinically significant fear of flying due to specific phobia or agoraphobia (N = 519). Methods: All participants underwent a standardized large-group one-session treatment (LG-OST) including psychoeducation, debriefing, and an in vivo exposure flight. Participants were randomized to one of four conditions targeting distinct mechanisms: peer support (SUPPORT), self-efficacy (SELF-EFFIC), expectancy violation (EXPECT), or coping with bodily fear symptoms (COPE). These mechanisms were reinforced prior and during paralleled exposure flights, conducted in separate aircraft per condition. Results: Across all conditions, LG-OST led to substantial symptom reduction short- and long-term. Fear ratings halved, over 50% flew again within the 6-month follow-up interval, and ∼70% no longer met diagnostic criteria. However, no condition yielded superior outcomes. While manipulation checks confirmed partial activation of target mechanisms (e.g., greater perceived peer support in SUPPORT, increased use of breathing techniques in COPE), these effects did not translate into differential clinical benefits. Conclusion: Findings support the efficacy and scalability of LG-OST, while suggesting that tailoring preparatory strategies to specific mechanisms may have limited added value. They also highlight the need to advance mechanistic research to better understand the intertwined processes underlying exposure success. Future work should focus on improving accessibility and sustaining long-term gains.