Table 2.

Overview of observational and process data studies (n=8).

Study	Number of participants	Intervention (duration)	Engagement strategy in intervention design	Recommended engagement strategy (author conclusion based on engagement rate)
Clarke et al, 2016 [18]	90	Assessment of users’ self-reported symptoms followed by 24×7 access to a personalized intervention that includes real-time self-monitoring of moods and interactive psychotherapeutic modules (7 weeks)	1. Reminders to facilitate self-monitoring by SMS text messaging or email as scheduled by the user; 2. Graphical feedback about self-monitoring	1. Personalized feedback incorporating program content; 2. Alerts and reminders; 3. Flexibility in agenda and use
Zarski et al, 2016 [20]	395	A total of 7 modules composed of psychoeducation and exercises for every module (4-7 weeks)	CGa: Received intervention; IGb1: Personalized written feedback from e-coach on the completed exercises and reminder by e-coach once in 7 days (content-focused guidance); IG2: Personalized feedback and adherence monitoring on demand of participants (adherence-focused guidance)	Content-focused guidance
Chou et al, 2017 [21]	—c	Gamified challenges in browser-based community forum; players can invite other players to browser-based community to form allies (4 weeks)	1. Gaming language; 2. Social forum; 3. Bright graphics	NRd
Dryman et al, 2017 [22]	3439	A total of 5 modules: learning through psychoeducation, core skill development by cognitive restructuring, 2 exposure modules, and final graduation module (12 weeks)	1. Coaches paired with users to provide feedback and support through weekly calls; 2. Coach-initiated and automated emails to encourage participation and progress	Guidance and support through coaching
Bakker et al, 2018 [24]	44	Assessment of user inputs on distress, followed by daily coping activities or games (30 days)	1. Games designed with real-time coping strategies; 2. Rewards for daily completed games; 3. Push notifications of incomplete games; 4. Bright graphics	NR
Morrison et al, 2018 [25]	543	Tools to improve awareness of participants’ thoughts or behaviors and support change in thinking patterns and behaviors (NR)	IG1: web based; IG2: mobile app; 1. Simple and reduced content; 2. Easy accessibility; 3. Push notifications for incomplete tool	IG2: 1. Simple and reduced content; 2. Easy accessibility; 3. Push notifications for incomplete tool
Song et al, 2018 [26]	3076	Self-help tools and a secure account with access to additional resources and links (NR)	NR	Personal email invitations to visit the site
Carter et al, 2019 [28]	5	Daily task, user-specific feedback, informational resources, self-assessment page, journal page (NR)	1. Self-monitoring tools for stress; 2. Goal setting with daily task; 3. User-specific feedback on stress level; 4. Reminders and progress summary	Task with user-specific feedback and self-monitoring

^aCG: control group.

^bIG: intervention group.

^cNot available.

^cNR: not reported.