A mobile app was developed from October 2023 to June 2024 to enhance the mental health of youth in out-of-home care. The app was created using the IM approach, which is a systematic method that integrates theoretical and empirical evidence to create impactful health promotion programs tailored to the needs of youth in out-of-home care [18]. It involves engaging stakeholders throughout the program development process to ensure that their perspectives and needs are considered [22]. It consists of six steps: (1) a logical model of the problem, (2) program outcomes and objectives (logical model of change), (3) program design, (4) program production, (5) program implementation plan, and (6) evaluation [18].

In the second step, we identified the expected outcomes from the results of Step 1. We defined the performance objectives for these outcomes and chose their determinants. A matrix was created to outline the change objectives that would impact the determinants and help achieve the performance objectives.

In Step 3, we conceptualized and designed the program, selecting theory- and evidence-based change methods to achieve the change objectives determined in Step 2. Theoretically, grounded change methods were translated into practical applications, with behavior change techniques (BCTs) [23] systematically applied. This phase focused on ensuring that each component of the program was based on evidence-based methods and tailored to meet the specific needs of youth in out-of-home care. Key tasks included identifying and selecting appropriate change methods based on established theories like the transtheoretical model (TTM), social cognitive theory (SCT), and elaboration likelihood model (ELM).

The TTM was chosen for its effectiveness in promoting behavior change through consciousness-raising and reinforcement management. Liu et al [24] demonstrated that TTM-based interventions help individuals understand the benefits of behavior change and maintain positive habits. By applying TTM, we aimed to support users in recognizing the value of structuring their daily routines and encouraging long-term adherence to healthy behaviors.

The SCT was incorporated for its focus on self-efficacy and observational learning. The theory postulates that internal processes, such as goal setting and self-efficacy, lead to behavioral outcomes [25], which informed our decision to apply SCT. This model supports users in setting goals, building self-efficacy, and learning emotion regulation strategies by observing others.

The ELM was selected to enhance emotional recognition through repeated exposure to emotional stimuli. Petty and Cacioppo [26] emphasized that repeated messaging can significantly influence attitudes and behavior, making ELM a suitable model for improving users’ emotional awareness and regulation. This theory helps explain how consistent exposure to emotional content can lead to deeper emotional understanding and behavior change.

These theoretical methods were then translated into practical applications by designing specific features within the mobile app to deliver the selected change methods effectively. We prioritized a user-centered design approach, as recommended by Johnson et al [27] and Bakker et al [28], for enhancing the app’s usage and effectiveness. The practical applications were developed to be user-friendly and engaging, allowing users to easily interact with the app and incorporate desired behaviors into their daily routines. The aim was to create a structured theoretical framework to help youth in out-of-home care manage their daily lives independently and improve their emotion regulation abilities.

Each component of the intervention app was developed systematically by integrating theoretical foundations, designing the user interface, and implementing functionalities. This step aimed to ensure the app’s practical applicability and functionality. Educational content, messages, and images depicting characters and emotions were also developed in a structured manner. An iterative development process was employed, working with the app development team to check and revise the prototype. Regular meetings were held with the lead app developer to communicate requirements, review screen designs, and discuss necessary modifications. These discussions were essential to consider and finalize the design modifications and ensure that the app met all the requirements.

The fifth step involved creating a comprehensive program implementation plan. This plan included strategies to ensure that the mobile app, which was designed to improve the mental health of youth in out-of-home care, was effectively adopted, used, and maintained over time.

The sixth step was to develop a plan to evaluate if the app had achieved its goals and objectives. This plan focused on conducting a thorough assessment of the app’s effectiveness, covering both process and outcome evaluations.

This study was approved by the Eulji University Institutional Review Board (approval EU23-43). Participants in the needs assessment interviews received detailed information about the study, and written consent was obtained before their participation. They were assured of their right to withdraw consent verbally at any stage of the interview, even after it had started, without facing any negative consequences. All collected data were anonymized and securely stored in encrypted files, accessible only to the research team. As an expression of gratitude, participants were offered a gift card worth 50,000 Korean won (approximately $35 USD).

Our literature review revealed that young people living in youth shelters often experience a high prevalence of mental health issues, like anxiety, depression, suicidal thoughts, and a poor quality of life [4]. After leaving youth shelters, they often experience isolation, loneliness, despair, and suicidal thoughts as they navigate the challenges of independent living [7].

Individual interviews were conducted with 5 adolescents aged 18-23 years who had been living in shelters for 5 months to 5 years. Many of the participants appeared to be either overweight or obese. Participants have experienced feelings of loneliness, depression, and, in some cases, suicidal thoughts. When facing difficult times, they sought support primarily from their romantic partners, peers, and shelter staff. When asked about their biggest concerns regarding independent living, financial stability was the primary worry, especially related to securing housing and managing living expenses after leaving the shelter. Day-to-day challenges, such as waking up on time and preparing meals, were significant concerns for many due to their limited experience in these areas. They described their current unstructured daily lifestyle—waking up late, spending most of their time lethargically in the shelter, and frequently looking at their smartphones. This reflects a lack of knowledge about healthy daily routines and the absence of motivation to maintain them (lack of knowledge about the advantages of daily routines, lack of motivation to structure daily routines). Psychologically, they expressed fears of dealing with loneliness after becoming independent. They mentioned that they would appreciate having a mobile app they could use daily, especially one that included visual elements like characters to make the experience more engaging.

Focus group interviews were conducted with shelter staff between the ages of 29 and 59 years, who had 1 to 9 years and 11 months of work experience. They specialized in counseling psychology, social welfare, youth education, counseling, and youth studies. The staff explained that the mental health of adolescents entering shelters recently was worse compared to those in the past, with many experiencing higher levels of depression and anxiety. Most adolescents spend the majority of their day on their phones, engaging in social media, calls, YouTube videos, and games. During their days off, they often wake up around 1-2 PM, have meals at the shelter, socialize with friends, and return just before bedtime. This indicates a lack of motivation to adopt healthy behaviors, such as exercise or balanced meals, and the absence of habits that support a healthy lifestyle (lack of knowledge about the importance of healthy behaviors, lack of habit in maintaining healthy behaviors).

The staff observed that some adolescents at the shelter have difficulties with emotional regulation, including depression and anxiety, and actively seek counseling. At times, some adolescents stay up past bedtime due to self-harm urges and turn to teachers for assistance. They also discussed how adolescents struggle to regulate their emotions even in the presence of peers and teachers. Furthermore, when these adolescents transition to living independently, they experience loneliness and depression, prompting them to seek support. This is connected to the lack of strategies for emotional regulation and the absence of motivation to implement those strategies consistently (lack of knowledge about emotional regulation strategies, lack of motivation to regulate emotions).

The staff mentioned that some adolescents struggle to manage their daily lives and emotions even after becoming independent. In some cases, they choose to return to the shelter. In addition, some adolescents do not maintain contact after leaving. Therefore, the staff suggested that a mobile app could assist youth in managing their daily lives and emotions postindependence. The program will help youth develop the knowledge and habits necessary for managing their emotions, as well as motivate them to consistently track and regulate their emotional states (lack of habit in tracking emotions, lack of acceptance of one’s emotions).

Out-of-home youth living in shelters encounter challenges due to a lack of support from family and caregivers, resulting in feelings of anxiety, depression, and a tendency to engage in self-injury. In their transition to independent living, many youth face loneliness, leading to feelings of powerlessness, difficulties in daily life management (lack of structured routines, poor habit formation), and struggles with emotional regulation (lack of emotional regulation strategies, lack of motivation). The proposed program aims to empower youth in out-of-home care to address these challenges by effectively managing their daily lives, regulating their emotions, and improving their stability and emotional well-being (Figure 1).

Based on the findings of the initial phase, the expected program outcomes were: (1) young people managing their daily lives independently and (2) young people enhancing their emotion regulation. Specific performance objectives for independently managing daily lives included structuring and maintaining daily routines, as well as developing healthy habits. In addition, performance objectives for enhancing emotion regulation in young people involved in expressing their emotions and implementing strategies for emotion regulation.

There is evidence that knowledge influences attitude, leading to behavioral changes. Habit formation is crucial for lasting behavioral change, especially when dealing with changing attitudes and temptations [29]. In this study, knowledge, attitude, and habits were chosen as determinants. For out-of-home youth with little family and adult support, forming habits is a key factor in being able to manage daily life and emotions independently. The change objectives are outlined for each of the four performance objectives in the three determinant areas (Table 1).

The theory-based program design and practical applications to achieve change objectives are detailed in Table 2. Core components of the program include structuring and maintaining routines, and regulating emotions delivered by a smartphone app. The design was based on behavioral change theories to provide users with tools to manage their daily lives and emotions. BCTs [23] were applied to operationalize the theoretical methods and provide structured guidance to users.

Consciousness-raising techniques from the TTM helped users understand the benefits of organizing routines and fostering healthy behaviors [30]. Emotion recognition was enhanced using the ELM through repeated exposure to emotion flashcards [26]. Observational learning from the SCT was applied by character models demonstrating emotion regulation [25].

To further enhance motivation, the SCT’s goal setting allowed users to establish routines and healthy behaviors independently, while verbal persuasion and supportive character models built confidence in emotion regulation. Self-monitoring and reinforcement strategies from the SCT and TTM supported habit formation and emotional regulation [31,32].

These theoretical methods were operationalized into practical strategies through the application of BCTs [23], including goal setting, self-monitoring, and reinforcement, which facilitated users in adopting and sustaining behavior changes in their daily routines.

The fourth step involved developing the specific components of the program to give it a viable form. To create an app for youth in out-of-home care, the program was designed by incorporating information gathered in Steps 1 to 3. Prototypes were utilized in designing the app’s structure and main features, focusing on making the interface intuitive and visually appealing for easy use by the youth. Figure 2 offers an overview of the mobile app’s user interface, showcasing the main components and navigation elements. It presents the home screen comprehensively, including the dashboard, navigation menu, and key interactive features like touchable buttons and icons.

Once users sign in and provide their information, they can use the app after obtaining approval from the administrator. Approved users receive guidance on using the app, including details regarding the importance of daily routines and healthy behaviors. Users then select a character to represent themselves and another character to act as their counselor. Subsequently, they set their daily routines, which include wake-up time, bedtime, number of outings per day, number of meals per day (at least 2), personal development activities (eg, reading, exercising, and studying), and household chores (eg, cleaning and washing dishes). The default home screen displays the current date and provides visual feedback, showing a cake image that is filled in based on routine completion. In addition, the calendar function allows users to visually track their daily achievements and serves as a self-monitoring tool to easily observe their progress.

During the day, users can input whether they completed their routines and the time spent doing so. They can then select their emotions from a list of 12 emoticons, along with appropriate verbal expressions. The counselor’s character provides messages based on the selected emotions to create an emotionally supportive environment. For instance, if a user chooses “anxious,” they receive advice such as, “Something is making you anxious. Consider the causes and prioritize tasks to write down. Talking or writing about your problems can help calm your negative emotions.” This can aid users in recognizing and managing their emotions.

The Emotion Regulation tab shows facial images gathered over a week in a graph, allowing users to visually monitor their emotional changes. In addition, users can write emotion diaries to document and analyze their feelings, aiding in improved understanding and management of emotions.

In the My Info tab, users can view basic information such as their characters, accumulated points, and set routines. They can also check and modify their routines at any time. The Settings tab offers options to change passwords, set notifications, and log out or reset accounts.

The development of the mobile intervention app followed a structured process that included defining requirements, screen planning, development, testing, and deployment. The development environment consisted of both a web-based system for data and user management and a mobile application. The mobile application was developed as a hybrid app designed for both Android and iOS platforms to maximize accessibility for users. The app was registered and made available through the Google Play Store and Apple App Store. User data was securely stored in the MySQL database, and the server was hosted on Amazon Web Services to ensure robust data protection. Security measures were carefully implemented to protect user information. User authentication was managed using JSON Web Token, providing a secure method for validating user sessions. All data transmissions were encrypted using SSL/TLS through the HTTPS protocol, ensuring that sensitive information remained protected during communication between the app and the server. In addition, server access control was strictly managed to further enhance security.

The fifth step is a detailed plan on how we envision the adoption, implementation, and long-term maintenance of the app within shelter settings. The program uses outcomes (adoption and implementation) that were developed with specific performance objectives for both the shelter staff and youth. Using normalization process theory [33], we identified changeable determinants that could influence the successful integration of the app into daily routines. These determinants were crossed with performance objectives to establish clear change objectives. The theoretical foundation for our strategies is based on BCTs [23], which informed the methods for fostering app adoption and ensuring its sustained use. Practical strategies include training sessions for staff, peer ambassador programs, and motivational tools for the youth, which were all designed to encourage continuous engagement with the app. Table 3 outlines the detailed performance objectives, change objectives, and corresponding strategies for both adoption and implementation.

The sixth step involved creating a detailed and comprehensive plan to evaluate the designed mobile app. This evaluation plan aims to systematically analyze the implementation process and effectiveness and identify areas for improvement, if necessary.

A mobile app was developed in this study to enhance the mental health of youth in out-of-home care using the IM approach. The app was created through a systematic and step-by-step development process.

Earlier studies have used the IM approach to create successful health promotion programs for different health concerns [19-21]. Nonetheless, IM-based mental health promotion initiatives aimed at youth residing in shelters are scarce. Furthermore, programs developed in previous studies frequently depend on brief interventions centered on in-person counseling, posing challenges in maintaining lasting impacts [12,17]. In South Korea, mental health apps such as MindLink [34] and Mind Café provide early intervention and emotional support to youth, but they are not specifically designed for youth residing in shelters. MindLink, for example, focuses on psychosis intervention, while Mind Café provides short-term emotional support through counseling, but it may be limited due to cost-related barriers to sustained access. These apps are valuable for their specific purposes but lack tailored features to address the unique needs of youth in out-of-home care. The mobile app developed in this study was created to overcome these limitations by providing accessible emotional support and daily management functions to youth. Emotion flashcards and self-monitoring tools assist users in recognizing and regulating their emotions independently, helping them cultivate their ability to self-manage even after leaving the shelter.

Our program was designed after conducting a comprehensive needs assessment of youth living in shelters. A previous study has emphasized the importance of a thorough needs assessment to improve program effectiveness [35]. This study investigated the behavioral and environmental factors influencing mental health issues by reviewing literature and interviewing youth in out-of-home care and shelter staff with the aim of providing tailored interventions.

We designed a program using theories like the TTM, SCT, and ELM to improve the scientific validity of the program’s mental health promotion program. By integrating these theories, our program identified knowledge, attitudes, and habit formation as key determinants, applying each theory’s methods to enhance the app’s effectiveness. Previous studies that incorporated these theories have shown positive outcomes.

We prioritized a user-centered design approach to enhance the app’s usage and effectiveness. To increase youth’s engagement and persistence, we implemented various strategies. For instance, users have the option to personalize their experience by selecting both their own character and their counselor’s character. The app’s user-friendly design, combined with a visual reward system for completing daily tasks, sparks interest and boosts engagement, encouraging continuous use. Users can establish their daily routines and receive visual cues indicating progress, such as a cake image that fills up as they complete tasks, providing a sense of achievement. When users choose an emotion from a list, the counselor responds with appropriate messages to foster emotional support. For example, if a user selects “anxious,” the counselor’s character might suggest, “Identify what’s causing your anxiety and focus on tackling simple tasks first. Acknowledging and addressing your problems can help alleviate negative feelings.” This feature enhances emotional support and equips users with tools to manage their emotions effectively. The Emotion Regulation section displays facial expressions accumulated over a week, allowing users to monitor changes in their emotions. By keeping emotion diaries, users can record and reflect on their feelings, which enhances their emotional awareness and regulation skills.

The interviews conducted during the needs assessment of this study’s development process focused on gathering real-world needs and collaborating with stakeholders. Therefore, insights obtained from these interviews were integrated iteratively, and any emergent trends were reviewed with the planning group. However, using formal analysis frameworks in future projects could enhance rigor and reliability. This study focused on developing a mobile app but did not confirm its effectiveness through application and evaluation. This limitation hinders the assessment of the app’s effectiveness and user satisfaction. Future research should validate the app’s long-term effectiveness in real-world scenarios. The study specifically targeted youth living in shelters in a specific region, limiting the generalizability of the findings to youth in other regions and cultural contexts. Further research is necessary to evaluate the app’s use among youth from various regions and cultural backgrounds.

This study outlines the development process of a mobile app aimed at enhancing the mental health of youth in out-of-home care using the IM approach. The app was created to assist youth in managing their daily lives and regulating their emotions independently, offering high accessibility and continuous support. The systematic development process and theoretical foundations for designing the app’s structure and features are described, along with plans for evaluating its process and effectiveness.

Although real-world use of the app was not evaluated in this study, the systematic approach and substantial stakeholder involvement in the development phase indicate its potential effectiveness. Future research should focus on assessing the app’s real-world usage and incorporating user feedback for continuous improvement. Additional studies are anticipated to establish a strong foundation for developing and implementing digital health interventions that can significantly improve the mental health and well-being of youth in out-of-home care.