Braver together: an exploration into the effectiveness of blended group cognitive behavior therapy as early intervention for socially anxious adolescents

Velthuizen S.L.M. (2025)

Doctoral Thesis

Social anxiety disorder is a highly persistent mental health problem with an average age of onset in early adolescence. Providing early intervention to adolescents with social anxiety disorder is crucial to prevent further deterioration and the subsequent development of comorbidities such as depression and alcohol abuse. We endeavored to provide effective early intervention to adolescents with social anxiety disorder and to boost group cognitive behavior therapy through the supplemental use of a therapy mobile app. Combined use of an online therapy platform with face-to-face treatment is known as blended therapy. In two meta-analyses, we studied the effectiveness of blended cognitive behavior therapy in internalizing disorders, studying the effect from before to after therapy and comparing blended cognitive behavior therapy to treatment as usual. We conducted blended group cognitive behavior therapy with adolescents ages 11-17, recruiting them from local schools rather than clinics to ensure intervention at an early stage. In a double-baseline design, we studied the efficacy of treatment through the lens of clinical impairment and through secondary outcomes such as self-perception, positive and negative cognitions, and public speaking anxiety. Participants conducted a public speaking task before and after treatment while wearing eye-tracking glasses. This allowed us to study their gaze behavior and speech disruptions during the speech, as well as their perception of the audience.

• Social anxiety disorder
• Adolescents
• Cognitive Behavior Therapy
• Early intervention
• Internalizing disorders
• Depression
• Meta-analysis
• mHealth
• Blended care
• Anxiety markers
• Gaze behavior
• Speech disruptions
• Audience perception

• All authors: Velthuizen S.L.M.
• Supervisor: Westenberg, P.M.
• Co-supervisor: Bos, E.J. van den; Miers, A.C.
• Committee: Hulst, H.E.; Klein, A.M.; Bexkens, A.; Masia Warner, C.; Nauta, M.H.; Perrin, S.
• Qualification: Doctor (dr.)
• Awarding Institution: Institute of Psychology, Faculty of Social and Behavioural Sciences, Leiden University
• Date: 2025-12-17