Efficacy of blended digital and face-to-face psychotherapy compared to enhanced psychotherapy for patients with Somatic Symptom Disorder (iSOMA+): study protocol for a multicenter randomized controlled pragmatic trial.

BACKGROUND: Persistent somatic symptoms (PSS) that occur in various somatic, functional, or mental health conditions can lead to considerable psychological distress and functional impairment. As such, they are a key characteristic of the Somatic Symptom Disorder (SSD) in DSM-5. While psychological treatments such as cognitive behavioral approaches can address these symptoms, their clinical efficacy in reducing symptom burden in previous trials remains limited. Blended psychotherapy, i.e., combining face-to-face psychotherapy with digital elements, is a promising new approach to efficiently enhance psychotherapeutic effects. This study therefore aims to evaluate the efficacy, mechanisms, and safety of blended psychotherapy compared to enhanced standard psychotherapy for individuals with SSD in outpatient psychotherapy.

METHODS: A two-armed, multicenter randomized controlled pragmatic trial will be conducted, and N = 250 adults with SSD will be randomized to either blended psychotherapy (20 individual sessions of cognitive behavioral therapy (CBT) + accompanying digital intervention; iSOMA+) or enhanced CBT (20 sessions of CBT + self-help booklet; CBT+). Participants are recruited at eight German university outpatient psychotherapy clinics. Assessments will be conducted at patient study inclusion (pre-treatment), during treatment, post-treatment, and 6 months follow-up. The primary outcome is the reduction in somatic symptom severity using the Screening for Somatoform Disorders (SOMS-7R) from baseline to post-treatment. Secondary outcomes include changes in symptom-related distress, coping, self-efficacy, as well as depression, anxiety, health anxiety, disability, quality of life, interpersonal relationship experiences and patient safety. Additionally, several potential moderators and mediators, including patient and intervention characteristics, will be examined.

DISCUSSION: This trial investigates the potential of blended CBT for improving treatment outcomes in patients with SSD and will provide evidence on the effects of active vs. passive self-help as treatment augmentation under pragmatic care conditions. By identifying prescriptive factors of treatment response, the study will support personalized care and contribute to more accessible and efficacious treatment options for patients with PSS.

TRIAL REGISTRATION: German Clinical Trials Register (DRKS) DRKS00035250. Registered on 13.06.2025, https://drks.de/search/de/trial/DRKS00035250 .