🧩 Without consistent reporting of engagement data, it's unfeasible to compare across studies
We call for:
🔸A standardised definition of engagement
🔸Standardised engagement metrics
🔸A structured framework to report engagement metrics & persuasive principles

💡 Persuasive design principles ranged from 1 to 12 per app (mode = 5)
📈But: No significant link between persuasive design and engagement or efficacy

Engagement reporting varied substantially across studies:
📊 25 different metrics identified
❓ 24% of studies didn’t report engagement at all

Most common metrics used:
% completing the intervention
% of modules completed

📱Apps improved outcomes compared to controls (g = 0.43, N = 16,728).
✅ Significant effects for depression, anxiety, stress, & eating/body image.
❌ No effect for psychosis, suicide/self-harm, postnatal depression, or general MH.
🔍 More research needed on less-studied areas.