A meta-analysis of persuasive design, engagement, and efficacy in 92 RCTs of mental health apps

This systematic review and meta-analysis examined the efficacy of digital mental health apps and the impact of persuasive design principles on intervention engagement and outcomes. Ninety-two RCTs and 16,728 participants were included in the meta-analyses. Findings indicate that apps significantly improved clinical outcomes compared to controls (g = 0.43). Persuasive design principles ranged from 1 to 12 per app (mode = 5). Engagement data were reported in 76% of studies, with 25 distinct engagement metrics identified, the most common being the percentage of users who completed the intervention and the average percentage of modules completed. No significant association was found between persuasive principles and either efficacy or engagement. With 25 distinct engagement metrics and 24% of studies not reporting engagement data, establishing overall engagement with mental health apps remains unfeasible. Standardising the definition of engagement and implementing a structured framework for reporting engagement metrics and persuasive design elements are essential steps toward advancing effective, engaging interventions in real-world settings.