Methods/design
depression, Anxiety, SAD
A within-between interaction design with randomization to one of three conditions will be used. In the APP condition, patients receive only the app without any additional contact with therapists, while in the TG-APP condition, therapists provide 8 sessions of video-based treatment in addition to using the app. The study will be conducted in two university outpatient treatment centers with reliably diagnosed SAD patients. The primary outcome will be defined as change in SAD symptoms, as measured by the Liebowitz Social Anxiety Scale (expert rating). Furthermore, a wide range of self-reports and clinician ratings for other symptoms (depression, general psychopathology) or quality of life will be used. A simulation-based power analysis for a 3 × 2 interaction effect (group × time) on the primary outcome in a linear mixed model resulted in a total sample size of 