Evaluation of a CBT-based program for mental health in the general population during the COVID-19 pandemic: a stepped-care approach using a chatbot and digitized group intervention - Langhammer, Till; Hilbert, Kevin 1987-; Wasenmueller,Robert; Praxl, Berit; Ertle, Andrea 1968-; Asbrand, Julia 1985-; Lüken, Ulrike 1976-; Langhammer, Till (Humboldt-Universität zu Berlin, 2025)