Investigating the Impact of Distress on the Effectiveness and Adherence to Ecological Momentary Interventions : A Micro-Randomised Trial

Background: Ecological Momentary Interventions (EMIs), including Just-in-Time Adaptive Interventions (JITAIs), offer timely mental health support. However, the optimal timing for delivery is debated. This study investigates the impact of distress levels at intervention times on EMI effectiveness and adherence. Method: A smartphone-based Micro-Randomized Trial (MRT) with 72 participants experiencing mild distress was conducted over 23 days. For the first week, participants completed brief Ecological Momentary Assessments (EMAs). From the second week, they engaged in EMIs alongside EMAs until the study's end. Data were analyzed using mixed-effects models. Results: EMIs significantly reduced distress during high-distress moments compared to low-distress ones (β = -0.27, p = .002). Adherence was similar across distress levels, but average-distress moments decreased EMI completion likelihood compared to low-distress moments (β = 0.65, p < .0001). High-distress moments showed significantly higher adherence than average-distress moments (β = 0.65, p < .0001). Conclusion: EMIs are most effective and have better adherence during high-distress moments, highlighting the importance of timing. Future research should continue to refine intervention timing to maximize benefits.