Pilot Randomized Controlled Trial of the Emotion Detectives In-Out: A Blended Version of the Unified Protocol for Transdiagnostic Treatment of Emotional Disorders in Children.

Anxiety disorders are highly prevalent in childhood, and increasing demand for services highlights the need for scalable and accessible interventions. This pilot randomized controlled equivalence trial examined the feasibility and preliminary efficacy of a blended adaptation of the Unified Protocol for Children ("Emotion Detectives In-Out"), integrating face-to-face group sessions with self-guided and therapist-supported online components. The intervention was compared with Coping Cat, a well-established cognitive-behavioral group program for childhood anxiety. Seventy-seven children aged 6-13 years with a primary anxiety disorder were randomized to either condition. Outcomes included clinician-rated severity and improvement, child- and parent-reported anxiety and depressive symptoms, and anxiety-related interference in daily life. Both interventions were associated with significant improvements over time across most outcomes. No significant between-group differences were observed for clinician-rated severity or improvement, and remission and treatment response rates were comparable. Significant group-by-time interaction effects favoring the blended intervention emerged for child-reported generalized anxiety, total anxiety and overall symptom scores. Between-group differences were limited, although Coping Cat was associated with significantly lower parent-reported family interference at post-treatment. Equivalence analyses yielded mixed findings, with some primary outcomes meeting the prespecified equivalence criteria. Findings provide preliminary evidence supporting the potential clinical utility of a blended transdiagnostic group intervention. Although several outcomes demonstrated statistical equivalence with Coping Cat, equivalence findings were mixed and should be interpreted cautiously given the pilot nature of the trial. Larger, adequately powered randomized controlled trials are needed to determine whether the interventions achieve clinically equivalent outcomes. Trial registration number: https://doi.org/10.17605/OSF.IO/62N4X (retrospectively registered at November 18, 2025).