Table 2.

Acceptability, feasibility, engagement, usefulness, accessibility, and outcomes.

Reference, year	App name	Measurement	Acceptability and feasibility	Engagement	Barriers to engagement	Perceived usefulness	Accessibility and inclusivity	Intervention outcomes
Bohleber et al [41], 2016	Companion App	Questionnaires and semistructured interviews	Adolescents regarded the concept of the app as well conceived, especially the peer-mentoring system. However, the app did not compare well to other available apps.	Engagement decreased markedly after the first 2 weeks. Average daily visits: in the first 2 weeks, 61; after 6 months, 8.	Technical problems, unclear benefits, and lack of time.	Content was judged informative and interesting. However, some reported that the purpose of app was not evident.	Unemployed participants suggested that reminders to use the app would help.	No significant effect on stress or the perception of social support.
Deady et al [42], 2020)	HeadGear	Questionnaires, semistructured interviews, and focus groups	Apprentices rated the app positively, (average 4/5 stars). Participants had no or neutral willingness to pay for the app. Most would widely recommend the app but predicted their own use would be infrequent (3-10 times) over the next 12 months.	Users completed approximately one-third of the app challenges.	Noncompletion of challenges attributed to “forgetting” and choosing not to “catch up.” Users wanted to be able to skip challenges and suggested gamification and greater personalization.	87.2% claimed it had at least moderately improved their mental fitness. Moderate impact on awareness, knowledge, attitudes, intention to change, help seeking, and behavior change around mental health and well-being.	Participants emphasized the importance of gamification and greater personalization, for example, through the inclusion of personalized music.	No significant differences between baseline and 3-month follow-up measurements. Engagement (intervention completion) directly related to effectiveness.
Fleming et al [43], 2017	Today!	Semistructured interview	Expressed enthusiasm for a comprehensive mobile phone app designed to treat clinically significant symptoms of anxiety and depression among young sexual minoritized men.	Not assessed in this paper.	Weekly phone calls with the coach was described by participants as a barrier to engagement.	Overall, participants had positive reactions to the app, but each individual found different features to be useful (eg, community resources and mood rater).	Usability testers had a wealth of suggestions for topics they would like to see addressed in this kind of app.	Not assessed in this paper.
Francis et al [44], 2020	CyFi Space	Questionnaire, group, and individual interviews	Acceptability of the app was rated moderate.	Overall, 37% recruitment response rate. 77% participants used the app at least once a week. Some participants indicated that the use of the app declined as the 6-week trial progressed.	40.9% reported watching the entertainment and motivational videos.	Many participants found the app both useful and fun to use and agreed they would. recommend the app to others.	Participants rated the app’s usability as high. Age-related accessibility measured.	Not assessed in this paper.
Geirhos et al [45], 2022	Minddistrict. Program: youthCOACHCD	Questionnaires	Content was perceived as appropriate. 58% would recommend intervention to a friend, 17% would likely recommend it, 17% would partly recommend it, and 8% would not recommend it.	Intervention adherence=40%, dropout=20%.	Not reported.	Individual tasks perceived as particularly helpful.	Not explicitly reported.	No symptom improvement. Small sample.
Glover et al [46], 2019	Pocket helper 2.0	Questionnaires	73% would recommend the program.	48% of the sample completed the 3-month assessment, while 19% completed the 6-month assessment.	Use and satisfaction with various features reported.	63% of participants at 3 months and 68% of participants at 6 months reported at least moderate benefit from intervention	Designed for youth experiencing homelessness based on the initial input from these youths and was refined based on the feedback received during a previous pilot trial.	Not assessed in this paper.
Gonsalves et al [47] , 2019	PODa Adventures	Focus group discussions, co-design workshops, and user testing	Service providers highlighted that self-help was not a culturally congruent concept for most Indian adolescents.	Not reported in this paper.	Following user testing, activities were shortened to be kept <2-minutes to minimize boredom and disengagement.	Problem-solving reported as being a useful and valued skill.	Design was sensitive to cultural context, language, participant media preferences, and digital access helped focus on user needs. Adaptations were made to address widespread literacy difficulties.	Not assessed in this paper.
Gonsalves et al [48], 2021	POD Adventures	Questionnaires and semistructured interviews	Satisfaction scores ranged from good to excellent.	Intervention completion rate was 92%.	App generally considered easy to use, but a few participants identified confusing game components and issues related to typing and difficult log-in passwords.	Most participants felt that the program had positively impacted their prioritized problem.	As reported in [47].	Outcomes at 4 weeks showed significant improvements on all measures.
Haug et al [49], 2017	Ready4life	Questionnaires	Large proportion of invited adolescents participated. Program evaluated as “very good” or “good” by 94.6% of participants.	Follow-up assessments were completed by 49.7% of the participants. Of the 39 program activities, the mean number carried out was 15.5. In total, 15% failed to engage in any activity, and 52% engaged in fewer than half of the activities.	Participation in the program was lower in male participants and among those reporting an immigrant background.	Not explicitly reported.	Not explicitly reported.	Statistically significant increases in targeted life skills, decline in at-risk alcohol use, and stable rates for tobacco and cannabis use.
Leonard et al [50], 2018	Calm Mom	Technology logs, questionnaires, and in-depth semistructured interviews	Participants felt the general content of app was highly relevant. 75% were “very” satisfied, and 18% were somewhat satisfied.	Mean of 14.77 minutes of using the app. Participants used at least one of the elements on the app on average on 44% of days when they had the study phone.	Technology challenges.	Supported their ability to effectively regulate their emotions.	Majority of participants noted that the app was very accessible, and several indicated that they felt less alone and felt genuinely cared for.	Not assessed in this paper.
Schueller et al [51], 2019	Pocket Helper, Purple Chill, and Slumber Time	Questionnaires	Satisfaction was high; 100% of participants would recommend the program, and 52% reported that they were very or extremely satisfied app.	57% of the participants completed all 3 sessions. Mean 2.09 sessions.	Mobile phone loss (through damage, theft, or other loss).	43% reported app as helpful; 48% found the skills they learned to be beneficial; 43% regularly used the skills.	The apps were preinstalled on all mobile phones before distribution to participants.	Participants experienced limited change on clinical outcomes with small effect sizes.
Escobar-Viera et al [52]a, 2023	REALbot	Questionnaires	High user satisfaction. Acceptability rated 5.3/7 but only 25% of participants described the app as exciting or leading edge.	42% of participants interacted with the app for 2 or more days.	Primary challenges were that app felt robotic and not smart enough.	Usability ratings were high on both measures.	Lack of voiceover feature.	Nonsignificant changes in scores of perceived isolation, depressive symptoms and social media self-efficacy.
Torok et al [53]a, 2022	LifeBuoy	Questionnaires	Not reported	71.5% completed 5 or more modules (completers)	Participants who completed first survey had significantly lower baseline anxiety symptoms compared to those who did not complete it.	Not reported	Not reported	Depression, anxiety, distress, and well-being symptoms improved in app group and control.
Yang and Chung [54]a, 2022	HARU ASD	Questionnaires	Acceptable scores in the Satisfaction and Usability Questionnaire.	No participants dropped out.	Not reported	Not reported	Not reported	Significant decrease in anxiety level, an increase in positive affect, and a decline in stereotypic behaviors, hyperactivity, noncompliance, and inappropriate speech.

^aStudies identified in the updated search.