Design, development, and evaluation of an mHealth app to reduce stress and promote happiness through smiling

The field of mental health application research is growing, yet comprehensive, long-term studies validating claims of stress reduction and mood enhancement are limited, with many apps lacking empirical evidence. The purpose of this study was to evaluate an mHealth application called SmileApp to promote positive mood as a means of reducing stress. The design of SmileApp is grounded in psychological theories and integrates artificial intelligence (AI) and persuasive technology (PT). To evaluate SmileApp, we conducted a two-week in-the-wild study involving 72 participants. This was followed by an optional semi-structured interview with 23 participants. Quantitative results suggest that SmileApp is usable, useful, and encourages users to smile more frequently. Furthermore, qualitative results suggest that SmileApp was a unique design to help users alleviate stress. These results offer valuable insights into innovative approaches for designing mHealth applications that promote positive mood. Moreover, the findings underscore the importance of utilising technology to support emotional well-being. We present a novel approach to promote desired behaviours by motivating users to read supportive messages and playing mobile games through the act of smiling.