Optimization of a Mobile Transdiagnostic Emotion Regulation Intervention for University Students: A Micro-Randomized Trial.

Increasing mental health problems among university students highlight the need for scalable, effective solutions. We have developed a transdiagnostic mobile intervention called ROOM, promoting adaptive emotion regulation (ER) skills among university students. Understanding how the intervention works and optimising content and delivery is essential for creating an effective and adaptive system. Therefore, this study aimed to optimise ROOM through a sequential explanatory mixed-methods design, combining a Micro-Randomized Trial (MRT), evaluating within-person effects using repeated randomisation, with user experience interviews. 161 university students (82% females) participated in a 3-week MRT to assess the intervention proximal outcomes, that is, participants' positive and negative emotional states after completing intervention exercises. Additionally, we evaluated impact on distal outcomes (i.e., distress symptoms and ER skills), and user experience by combining objective (e.g., exercise completion rates) and subjective (e.g., exercise likability and helpfulness ratings) engagement patterns with insights from the semi-structured interviews (n = 18). Upon receiving the intervention, positive emotional states increased and negative ones decreased. The effect on positive emotional states gradually decreased over time while the effect on negative emotional states remained stable throughout the 3-week intervention period. Distress symptoms and ER skills either remained stable or improved over the 3 weeks, which indicated the intervention's safety. Overall, engagement patterns and interview data show that the intervention was well received, students enjoyed this study design and found context-sensitive content recommendations highly relevant.