Internet-Based Self-Help Treatment for Panic Disorder with Minimal Therapist Contact: A Randomized Controlled Trial in a Spanish Clinical Population

Jorge Orrego — [email protected] · [email protected]:0009-0000-6429-4552 (J. Orrego Bravo)Trial registration:ClinicalTrials.gov NCT02402322Open dataset:https://doi.org/10.5281/zenodo.20084725 (CC BY 4.0)Funding:Start-Up Chile (CORFO), Government of Chile; Amindterapia.comData collection:In collaboration with Universitat Autònoma de Barcelona (UAB)Conflicts of interest:J. Orrego is co-founder of Amindterapia (holds Spanish adaptation license for Free from Anxiety). R. Raich Escursell declares no conflicts of interest.ABSTRACTBackground. Internet-based cognitive behavioral therapy (iCBT) represents a scalable response to the substantial treatment gap in panic disorder (PD). The efficacy of minimal-contact formats remains underspecified in Spanish-speaking clinical populations.Method. Ninety-five adults meeting DSM-IV-TR criteria for PD were randomized to an 8-week iCBT program (Free from Anxiety) with optional email support (n = 49) or a waiting-list control (n = 46). The primary outcome was PD severity (PDSS); secondary outcomes included anxiety sensitivity (ASI-3), general anxiety (BAI), and depression (BDI-II). Assessments at pre-treatment, post-treatment (8 weeks), and six-month follow-up. Trial registration: ClinicalTrials.gov NCT02402322. Anonymized data available at: https://doi.org/10.5281/zenodo.20084725 (CC BY 4.0).Results. Large improvements relative to controls (mean between-group d = 1.30; all 95% CIs excluding zero). Sensitivity ITT analyses confirmed robustness (d = 0.47–1.47). Mediation analysis showed 27.4% of the treatment effect on PDSS mediated by ASI-3 change (indirect effect = 1.85, 95% bootstrap CI [0.36, 3.70]). Gains fully maintained at six months (d = 1.59).Conclusions. Minimal-contact iCBT produces large and durable effects in a Spanish clinical population with high comorbidity, supporting its viability as a first-step intervention within stepped-care pathways. Keywords: panic disorder · iCBT · minimal therapist contact · stepped care · anxiety sensitivity · mediation analysis · Spain · RCT