Transdiagnostic Group Treatment of Emotional Disorders: A Cross-sectional and Naturalistic Study of Outcome, Change Processes, and Clinical Training

Background Anxiety and depression are the most common mental disorders, incurring vast personal and societal costs. While effective evidence-based treatments exist, healthcare systems struggle to meet the growing demand for services. A key challenge in delivering care is that most treatments are diagnosis specific. This complicates training and implementation due to clinicians having to learn multiple treatment manuals. In addition, these single-disorder treatments may also often have poor applicability to the complex symptoms and patterns of comorbidity typically seen in real-world clinical settings. As a response to these challenges, several transdiagnostic treatment protocols have been developed to target psychological processes underlying different diagnoses. One such model is the "Unified Protocol for Transdiagnostic Treatment of Emotional Disorders" (UP) developed by David Barlow and colleagues. UP addresses the functional processes that maintain emotional disorders, such as negative reactions to emotions and avoidance behaviors.

The Unified Protocol (UP) has shown non-inferiority to diagnosis-specific CBT and superiority to treatment as usual in both individual and group formats. Meta-analyses confirm its effectiveness for comorbid emotional disorders and suggest potential for cost-effective, scalable implementation.

Knowledge gaps

• Norwegian Setting: Only one small feasibility study of UP has been conducted in Norway. A larger naturalistic trial is needed to assess outcomes (quality of life, functioning, symptoms) and potential negative effects in a public health context.
• Processes of Change: More research is needed to identify active treatment mechanisms (e.g., emotion regulation, mindfulness, cognitive flexibility) and their association with outcomes in group UP. Non-specific factors such as credibility and group alliance also require investigation.
• Psychophysiological Measures: UP's impact on objective emotion regulation markers (e.g., heart rate variability, interoception) is unexplored. Inclusion of such measures can reduce bias and clarify underlying mechanisms.
• Novice Therapists: The ability of graduate psychology students to deliver UP with high fidelity in group format remains unclear and merits further investigation.

Study objectives This study aims to explore outcomes, processes of change, and user experiences of UP group treatment for patients with emotional disorders in a naturalistic clinical sample in a Norwegian setting. Additionally, it will compare the clinical sample to a healthy control group to better understand how transdiagnostic characteristics serve as vulnerability or resilience factors in the development of emotional disorders. Lastly, the study examines whether novice therapists can be trained to deliver the treatment with high levels of fidelity based on ratings of adherence and competence.