Internet-based indicated prevention of anxiety and depression disorder onset three-arm randomized clinical trial

Preventing mental disorders is important to avoiding clinical conditions. This study evaluated the efficacy of internet-based indicated prevention for anxiety and depressive disorders. In a three-arm randomized controlled trial, 566 adults with subthreshold anxiety (GAD-7 ≥ 5) and/or depressive symptoms (CES-D ≥ 16), but no clinical diagnosis in the past six months (MINI 6.0), were assigned to either an individually (IG-IMI, n = 186) or automatically (AG-IMI, n = 189) guided digital intervention, or waitlist control (WLC, n = 191). The digital intervention comprised 8 transdiagnostic, self-tailored, CBT-based sessions. The primary outcome was time to onset of any anxiety or depressive disorder over 12 months, assessed via blinded diagnostic interviews (MINI). AD/DD onset was 19.4% in IG-IMI, 14.8% in AG-IMI, and 30.9% in WLC. Cumulative incidence was 23.1% (IG-IMI), 20.7% (AG-IMI), and 36.0% (WLC; p < 0.001). Hazard ratios were 0.59 and 0.47; NNTs were 7.76 and 5.79. Both individually guided and automated interventions effectively reduced AD/DD incidence. Trial Registration: The study was preregistered in the German Clinical Trial Registration (DRKS00011099; https://drks.de/search/de/trial/DRKS00011099 ).