Young adults face increasing stress and anxiety due to academic pressures, social media, and relationship challenges, leading to burnout and mental health issues. Practicing gratitude offers a potential solution, demonstrated to improve mental and physical health, relationships, and life satisfaction. However, incorporating gratitude into daily life can be difficult due to unfamiliarity, lack of guidance, and time constraints. Existing gratitude applications often lack a user-centered design approach, prioritizing clinical expertise over user input, potentially failing to meet user needs and daily routines. This study aims to address this gap by using a UCD approach to develop a mobile application for promoting gratitude among young adults. The research questions are: 1) What are the key features of a mobile application that could promote regular gratitude practice among young adults? 2) What are the perceived benefits of using such applications among young adults, and how do these benefits vary based on users' engagement levels? The ubiquity of smartphones makes mobile applications an ideal platform for accessible and convenient engagement.

The literature review establishes the positive impact of gratitude on wellbeing, citing numerous studies showing its correlation with reduced anxiety, depression, and loneliness, as well as improved stress coping and stronger social bonds. It then surveys existing interventions, both offline (journals, letters, acts of kindness) and online (mobile apps, web-based journals, social media). While online interventions are growing, many lack user-centered design, prioritizing expert opinion over user needs and preferences. The review emphasizes the importance of a user-centered design (UCD) approach in developing effective digital mental health interventions, citing examples where UCD has successfully identified key features for various applications catering to young adults' needs and preferences.

The research involved two studies: a formative study and a deployment study. The formative study recruited 20 young adults (10 women, 10 men, mean age 21.2) who used existing gratitude applications for two weeks. Qualitative interviews explored their preferences for structuring gratitude expressions, the importance of prompts, and the role of timing and social contexts. Two highly-rated applications (Delightful - Three Good Things and Gratitude 365) were selected based on simplicity, gender neutrality, high ratings, free availability, and comparable design across iOS and Android. Thematic analysis was used to analyze interview data. The deployment study recruited 26 young adults (16 women, 9 men, 1 non-binary; mean age 22.3), randomly assigned to an experimental group (with predefined gratitude categories) or a control group (without categories). Participants used a custom-developed application for two weeks, providing quantitative engagement data (word count, mood change) and qualitative interview feedback. The custom application included features informed by the formative study: daily 6 PM reminders, mood labeling before and after entries, and (in the experimental group) structured life area options based on the PERMA model. Quantitative data included word counts, mood changes (measured on a 1-5 scale), and perceived motivation, engagement, and usefulness (1-7 Likert scale). Qualitative data from both studies were analyzed using thematic analysis.

The formative study revealed a need for structured support, examples, and explanations within gratitude applications, particularly for first-time users. Participants preferred using the application alone, in the evening, emphasizing privacy. Mood labeling before and after gratitude practice was seen as beneficial for self-awareness and identifying triggers. The deployment study showed that participants in the experimental group (with structured options) had significantly higher word counts per entry (15.27 ±2.42) compared to the control group (8.90 ± 0.83). The experimental group also showed a greater increase in mood per entry (0.64±0.04) than the control group (0.56±0.05). Retention rates were similar across groups (79.1% vs. 76.4%). Qualitative data from the deployment study confirmed the benefits of structured prompts and evening reminders, but also revealed concerns about the frequency of mood labeling—some found it overwhelming. Importantly, participants reported positive shifts in perception, increased resilience, and the benefits of even passive engagement (simply contemplating positive aspects). The practice of gratitude extended beyond the application into daily life and social interactions.

The findings address the research questions by identifying key features (structured options, evening prompts, mood labeling) and perceived benefits (positive shifts in perception, increased resilience, community building) of gratitude applications. The higher engagement in the experimental group suggests that structured options facilitate deeper and more meaningful reflection. The consistent notification timing supports habit formation, aligning with principles of just-in-time adaptive interventions (JITAIs). While mood labeling is valuable, its frequency requires careful consideration to avoid overwhelming users. The observation of benefits from passive engagement highlights the need for flexible design, accommodating various engagement levels. The extension of gratitude practice into daily life and social interactions underscores the potential for these applications to positively impact mental health and relationships. The study provides valuable insights for HCI and CSCW, demonstrating how UCD can effectively support gratitude practices in young adults’ daily lives.

This study identified key features for effective gratitude-promoting mobile applications in young adults, including structured options, evening prompts, and mindful mood labeling. It demonstrated the positive impact of these features on engagement and perceived benefits, such as positive shifts in perception, increased resilience, and the extension of gratitude to daily life and social interactions. Future research should explore broader geographical contexts, incorporate objective measures, and investigate alternative designs for personalization and engagement.

The study's geographical limitations (Europe and North America) may limit generalizability. The reliance on self-reported measures introduces potential biases. The design space explored was not exhaustive; future work could explore alternative approaches and deeper personalization.