Comparing an Internet-delivered Cognitive-Behavioral Therapy for Prolonged Grief Disorder in blended format versus self-applied supported by Ecological Momentary Assessment and Ecological Momentary Intervention: Study Protocol for a Randomized Controlled Trial. (Preprint)

BACKGROUND Prolonged grief disorder (PGD) is associated with persistent grief symptoms and significant impairment in daily functioning. Although evidence-based psychological treatments are effective, access to specialized bereavement care remains limited. Internet-based interventions may increase access to psychological support, although feasibility studies have shown higher dropout rates in the self-administered condition, highlighting the need for strategies to improve treatment engagement and adherence. Smartphone-based Ecological Momentary Assessment (EMA) and Ecological Momentary Intervention (EMI) tools may help address this challenge by enabling real-time assessment and providing support in patients’ natural environments. However, the application of these approaches to PGD remains limited. OBJECTIVE This study aims to evaluate the efficacy of two delivery formats of the internet-based GROw intervention for PGD: a blended format combining GROw with videoconference-delivered therapist support (BF-GROw) and a self-applied format supported by a mobile app delivering Ecological Momentary Interventions and Assessments (iGROw), compared with a waitlist control group. The study will also examine the feasibility and acceptability of both intervention formats, including treatment adherence, engagement, satisfaction, usability, treatment preferences, and reasons for treatment discontinuation. METHODS This three-arm, single-blind randomized controlled trial will include adults diagnosed with PGD who will be randomly allocated to each study condition. Both intervention groups will receive access to the internet-based GROw program. BF-GROw will additionally include individual videoconference sessions with a therapist every 10–12 days, whereas iGROw will be fully self-applied and supported by a mobile app incorporating EMAs and EMIs. Participants will be assessed at baseline, post-treatment, and at 3- and 12-month follow-ups. The intervention is expected to last 8 to 14 weeks. The WL group will complete the pre- and post-treatment assessments, and participants will be assigned to the iGROw treatment condition after completing the waitlist period (10 to 12 weeks). RESULTS Participant recruitment started in December 2025 and is currently ongoing. Participant allocation to the study conditions and data collection are also ongoing. Data analysis will begin after completion of data collection. CONCLUSIONS This study may contribute to the development of more accessible and personalized psychological interventions for PGD by providing evidence on different treatment delivery approaches. The integration of smartphone-based EMA and EMI tools may further support the delivery of therapeutic support in patients’ everyday environments and inform the development of scalable digital interventions for PGD. CLINICALTRIAL The study is registered at ClinicalTrials.gov (NCT06932120).