Effectiveness and cost-effectiveness of an online transdiagnostic positive psychology intervention for patients awaiting mental health treatment and their loved ones: study protocol.

BACKGROUND: Mental healthcare is under pressure, resulting in prolonged waiting lists for treatment. This is problematic, as time spent on a waiting list is associated with suboptimal recovery, more treatment dropout, and increased societal costs. An online transdiagnostic positive psychology intervention (eHealth PPI) may increase resilience (i.e., the ability to adapt to challenging experiences) and well-being among patients. Offering the same intervention to loved ones could be a novel contribution to enhancing positive effects among patients and loved ones. A study protocol is presented aimed at examining the clinical effectiveness, cost-effectiveness and implementation procedures of an eHealth PPI for patients with various mental health complaints awaiting treatment and their loved ones. METHODS: Using two studies, the current manuscript proposes a threefold evaluation of an eHealth PPI consisting of 9 modules, focusing on: [1] clinical effectiveness, [2] economic evaluation, and [3] implementation procedures. To evaluate the procedural implementation of the eHealth PPI from a user-perspective, a replicated single-case design (RSCD) will be performed in study 1, with measurements at baseline, after each module, and post-intervention. In study 2, a randomized controlled trial (RCT) will be used to examine the clinical effectiveness, cost-effectiveness and implementation procedures of the eHealth PPI, using three arms: [1] PPI during the waiting period for patients, [2] PPI during the waiting period for patients and loved ones, and [3] treatment as usual (TAU), i.e., the conventional waiting period for patients. Following the waiting period, patients will receive a mental health treatment as usual. Study 2 will employ measurements at baseline, post-intervention, after 3, 6, and 9 months, 1 year following PPI completion, and 1 year following treatment completion. A key outcome is positive mental health, consisting of emotional, social, and psychological wellbeing. Other outcomes include, for instance, resilience, psychological complaints, quality of life, societal costs, and adherence. DISCUSSION: Introducing a transdiagnostic eHealth PPI to various patients awaiting mental health treatment and their loved ones may improve treatment outcomes. Enhancing resilience through an eHealth PPI may reduce healthcare costs and health-related societal costs, potentially making it a cost-effective strategy compared to TAU. TRIAL REGISTRATION: NL-OMON57370. Registered in the Overview of Medical Research in the Netherlands on 17 March 2025.