Development of a Digital Multimodal Pain Intervention (CHRONIC): Protocol for a Randomized Controlled Trial Study.

Background: Chronic pain affects approximately 12 million individuals in Germany and significantly impairs quality of life. Although multimodal treatment approaches-combining physical, psychological, and behavioral strategies-are considered the gold standard, access to specialized multidisciplinary pain treatment, including physiotherapy and psychological interventions, is often hampered by long waiting times, which highlights the need for scalable, low-threshold treatment options. Digital health interventions, particularly those grounded in established therapeutic models, offer a promising solution to bridge this treatment gap. The German Digital Health Care Act has opened pathways for reimbursable digital applications, such as CHRONIC, which is grounded in acceptance and commitment therapy as a third-wave cognitive behavioral therapy framework and integrates selected cognitive behavioral techniques, mindfulness-based strategies, and physiotherapy into a structured web-based program. Objective: This study protocol outlines a randomized controlled trial (RCT) aimed at evaluating the effectiveness of CHRONIC, a 12-week web-based, multimodal self-help program for individuals with chronic pain, with a focus on reducing pain intensity, reducing pain-related interference, and improving quality of life. Methods: This is a monocentric, 3-arm RCT with assessments up to 6 months after baseline. A total of 200 participants with chronic nonmalignant pain will be randomized into one of three groups: (1) intervention with individualized psychological feedback, (2) intervention with standardized computer-generated feedback, and (3) treatment-as-usual waitlist control. Weekly modules in the intervention arms include psychotherapeutic video sessions, interactive acceptance and commitment therapy-based and cognitive behavioral therapy-based exercises, mindfulness practices, and physiotherapeutic training. Outcomes will be assessed via validated self-report instruments: West Haven-Yale Multidimensional Pain Inventory for pain intensity and interference, Assessment of Quality of Life-8 Dimensions for quality of life, German version of Chronic Pain Acceptance Questionnaire for pain acceptance, Patient Health Questionnaire-9, German version for depression, and Generalized Anxiety Disorder 7-item Scale for anxiety. Data will be analyzed using mixed models for repeated measures based on the matched ~6-month assessment. Missing data will be addressed using multiple imputation. Results: Recruitment started in January 2026 and is projected to end in July 2026. As of January 22, 2026, 18 participants had been enrolled. Primary end point data collection is expected to be completed in January 2027, with primary analyses and dissemination planned for 2027. Conclusions: This study protocol describes an RCT designed to evaluate the clinical utility of CHRONIC as a scalable, low-threshold intervention for chronic pain. CHRONIC aims to address the multifactorial nature of chronic pain by integrating psychotherapeutic, physiotherapeutic, and mindfulness-based strategies into a single digital program. Future studies will be required to determine how this multimodal format compares to unimodal interventions. The findings aim to inform future digital health developments and contribute to the implementation of biopsychosocial care models in routine practice.