Written-Exposure Therapy for Transdiagnostic Anxiety Symptoms: Treatment Efficacy and Mechanisms of Change

In this study, we investigate mechanisms underlying transdiagnostic written-exposure therapy (WET), a novel, scalable, online intervention for pathological-anxiety symptoms. In a randomized controlled trial with 89 participants, WET produced significant anxiety reduction that continued through 2-month follow-up (standardized mean difference [SMD] = 0.85). We systematically evaluated multiple potential mechanisms across cognitive, emotional, and behavioral domains. From this broad assessment, two candidate mechanisms emerged as both significantly affected by treatment and correlated with symptom improvement: enhanced distress tolerance (r = –.35) and decreased anxious responses to core threats (r = .39). This suggests exposure therapy might operate through dual pathways: improving distress tolerance and reducing anxious responses. A neutral-imagery control condition showed immediate but nonsustained anxiety reduction and actually decreased distress tolerance, revealing distinct therapeutic trajectories between neutral-imagery-based versus exposure-based interventions. This research advances understanding of mechanisms of exposure while highlighting specific targets for enhancing interventions.