The Effects of a Digital, Transdiagnostic, Clinically and Peer-Moderated Treatment Platform for Young People With Emerging Mental Health Complaints: Repeated Measures Within-Subjects Study - Marilon van Doorn; Anne Monsanto; Chen Lu Wang; Sander C J Verfaillie; Thérèse A M J van Amelsvoort; Arne Popma; Monique W M Jaspers; Ferko Öry; Mario Alvarez-Jimenez; John F Gleeson; Dorien H Nieman (JMIR mHealth and uHealth, 2023)