Mental health INtervention with Digital APPlications (MIND-APP): Protocol for a Randomized Controlled Researcher Blinded Trial Evaluating the Effectiveness of the Tankevirus and Grubl Mental Health Apps Compared to a Placebo App: A Stage 1 Registered Report (Preprint)

BACKGROUND Anxiety and depression impose substantial clinical and economic burdens worldwide, with high prevalence, impaired functioning, and elevated health care costs. Digital self-help interventions offer scalable and potentially cost-effective strategies, yet evidence from rigorously controlled economic evaluations remains sparse. OBJECTIVE This trial aims to evaluate the effectiveness and cost-effectiveness of two Norwegian mental health apps—Tankevirus (cognitive behavioural therapy-based) and Grubl (metacognitive therapy-based)—compared to a digital placebo in reducing anxiety and depression symptoms, improving health-related quality of life, and generating quality-adjusted life years (QALYs). METHODS The MIND-APP trial is a three-arm randomized controlled trial (1:1:1 allocation) conducted fully remotely via a bespoke smartphone research platform. A total of 1,000 Norwegian residents aged ≥16 years with mild to moderate anxiety and/or depression will be recruited through national digital outreach. Co-primary outcomes are changes in anxiety (GAD-7) and depression (PHQ-9) scores from baseline to post-intervention (4 weeks). Secondary outcomes include health-related quality of life (EQ-5D-5L), QALYs accrued over 6 months, functional impairment (WSAS), health care resource use, and adverse events. Incremental cost-effectiveness ratios (ICERs) for Tankevirus and Grubl relative to placebo will be estimated from the perspective of public health services. RESULTS Funding was secured in April 2025, with ethical approvals, licensing, and app development planned through 2026. Recruitment will commence in late 2026 with follow-up through 2027. Results will provide robust evidence on the clinical and economic value of scalable app-based interventions for common mental health disorders. CONCLUSIONS This trial will be among the first large-scale registered reports to combine rigorous clinical and economic evaluation of digital mental health interventions. Findings will inform health policy and resource allocation by determining whether low-cost, app-based programs represent cost-effective solutions for reducing the burden of anxiety and depression. CLINICALTRIAL To be registered at DRKS (primary registration) and ClinicalTrials.gov for visibility.