. 2022 Jun 1;8:20552076221098268. doi: 10.1177/20552076221098268

Table 1.

Characteristics of included studies.

First author, Country	DMHI name, characteristics	Primary outcome(s) & data collection time points	Study design	Treatment (Engagement strategy) arm(s)	Participant demographics*	Comparator arm(s)	Engagement strategy details	Engagement measure
Batterham et al.²⁶, Australia	myCompass 2 14 modules, 7 weeks. Unguided. 7 modules provided core transdiagnostic CBT, whereas the other 7 provided content aimed at addressing specific mental health problems.	Depression- and anxiety-related symptoms Post: 7 weeks Follow-up: 19.1 weeks	RCT	Engagement Facilitation Intervention (EFI, n = 280)	Adults from the general population. EFI group: 54.3% aged between 36 −55yrs. 77.5% female No EFI group: 57.9% aged between 36–55yrs. 76.1% female	No strategy (n = 285)	The EFI was developed using a participatory design approach that involved potential end users. It consisted of brief, tailored, written, and audio-visual content with the following: - Feedback about the participant's symptom levels - Tailored description of the benefits of participating in DMHIs - Information about the characteristics and efficacy of myCompass 2 Provided to participants on an Internet-based platform after randomisation and before starting on myCompass 2	Modules started Modules completed
Beintner et al.²⁷, Germany	IN@. CBT. 11 sessions, 39.1 weeks. Unguided. Reading assignments, email feedback, online chat with psychologist	Symptoms of bulimia nervosa (BN) Post: 39.1 weeks Follow-up: NA	Quasi	Telephone prompts (n = 63)	Adults diagnosed with BN, and receiving inpatient treatment. 25.8(7.09) yrs 100% female	Email prompts (n = 63)	5-min calls by a research assistant at 6 time-points: 2 weeks, 2-, 3-, 4-, 6-, 8-months post-allocation.	% of all assignments completed
Berger et al.²⁸, Switzerland	Internet-based self-help guide. CBT 5 lessons, 10 weeks. Unguided. Text-based lessons, several exercises, online diary, online discussion forum.	Symptoms of social phobia Post: 10 weeks Follow-up: 26.1 weeks	RCT	Emails – standard (n = 27) Emails – optional (n = 27)	Adults aged 18 and above. Self-report meeting cut-off on at least 1 of 2 social anxiety measures. Email: 36.9(11.6)yrs 48.1% Female On-demand: 37.4(11.4)yrs 55.6% Female	No strategy (n = 27)	Email support: Weekly email feedback by therapist Access to email contact with therapist Optional: start with no emails. Provision of support upon request	Lessons completed
Berger et al.²⁹, Switzerland & Germany	Deprexis. CBT 11 modules, 10 weeks. Unguided. Each module imparts concepts and techniques, engages the user through exercises and response prompts.	Depression-related symptoms Post: 10 weeks Follow-up: 26.1 weeks	RCT	Email prompts (n = 25)	Adults aged 18 and above. Self-reporting at least mild depressive symptoms 38.2(15.1)yrs 68% Female	No strategy (n = 25)	Weekly therapist emails with feedback based on participants’ program usage over the previous week.	Modules completed
Bidargaddi et al.³⁰, Australia	JOOL. Behaviour modification. 12 weeks. Unguided. Feedback and content recommendations are provided based on user's self-monitoring ratings.	General mental well-being Post: NA Follow-up: NA	Micro-randomised trial	All participants with push notifications enabled (n = 1255)	Adults. Office workers Age (yrs): <30: 28.9% 30–50: 42.4% >50: 28.7% 64.0% Female	NA	Time-varying push notifications containing a contextually tailored message from a curated library to Push notifications randomised could be sent at 1 of 6 chosen time points throughout the day. Maximum of one message per day.	% who used app within 24hrs of receiving notification
Bidargaddi et al. (2018b)³¹, Australia	JOOL. Behaviour modification. 12 weeks. Unguided. Feedback and content recommendations are provided based on user's self-monitoring ratings.	General mental well-being Post: NA Follow-up: NA	Micro-randomised trial	All participants with push notifications enabled (n = 1265)	Adults. Office workers Age (yrs): <30: 28.9% 30–50: 42.4% >50: 28.7% 64.0% Female	NA	Tailored suggestions vs. tailored insights.	% who used app within 24hrs of receiving notification
Carolan et al.³², UK	WorkGuru CBT, positive psychology, mindfulness 7 modules ( + 3 optional), 8 weeks. Unguided.	General mental well-being Post: 8 weeks Follow-up: 8 weeks	RCT	Online discussion group (n = 26)	Adults. Aged 18 and above; working in a UK-based organisation. Elevated stress levels 40.2(9.8)yrs 81% Female	No strategy (n = 28)	Online discussion group that was delivered via a bulletin board. Facilitated by a coach, who introduced one or more of the modules and encouraged discussion about the topic each week. Participants remained anonymous.	1. No. of site logins 2. Modules completed 3. Page views
Cheung et al.³³, USA	IntelliCare. Behavioural Intervention Technology model. 12 apps; 16 weeks. Unguided.	Depression- and anxiety-related symptoms. Post: NA Follow-up: NA	Quasi-experimental	Recommender app (“Hub”; n = 1514)	Adult 36(13)yrs 62% Female	No strategy (n = 3047)	Hub coordinates user experience with the other IntelliCare apps, including managing messages and notifications from the other clinical apps within the IntelliCare suite and encourage exploration of new apps.	1. Time between DL and last use 2. # sessions launched (any app) 3. # days/week with at least one session
Clarke et al.³⁴, USA	ODIN (Overcoming Depression on the InterNet). Pure self-help program offering training in cognitive restructuring. Each chapter presents a new technique via interactive examples and practices 7 chapters, 16 weeks max. Unguided.	Depression-related symptoms Post: 16 weeks Follow-up: NA	RCT	Telephone prompt (n = 80)	Adults. Recruited both clinical and non-clinical populations. Identified using electronic medical records 44.4(10.5)yrs 83.8% Female	Postcard prompt (n = 75)	The telephone reminder calls were <5 min and scripted to convey information identical to that included on the postcard reminders. Reminder staff had no mental health background, were prohibited from engaging in any therapy-like activity, and could only assist users with basic website troubleshooting.	Frequency of log-ons.
Farrer et al.³⁵, Australia	BluePages is a psychoeducational website that contains information and resources related to depression. (Week 1) AND MoodGym: online CBT program for depression. Five interactive modules released sequentially. (Weeks 2-6). Unguided.	Depression-related symptoms Post: 6 weeks Follow-up: 26.1 weeks	RCT	Telephone tracking (n = 45)	Adults (18 years and above) who called into a suicide counselling hotline. > 22 or above on the Kessler Psychological Distress Scale (K10) 41.7(12.1)yrs 82% Female	No strategy (n = 38)	Weekly 10-min telephone call from a lay telephone counsellor, with the call addressing any issues related to participants’ use of the online programs.	1. Visits to the BluePages site. 2. MoodGYM program modules completed (0 to 5) 3. % participants that completed all learning activities
Gilbody et al.³⁶, UK	MoodGYM. CBT five interactive modules released sequentially and a sixth session that is predominantly consolidation. 5 weeks. Unguided.	Depression-related symptoms Post: 17.4 weeks Follow-up: 34.8 weeks	RCT	Telephone facilitation (n = 187)	Adults recruited from primary care. >10 for depression (PHQ9) 41.0(13.8)yrs 66.8% Female	No strategy (n = 182)	8 telephone calls conducted by a telephone support worker alongside the cCBT program within 14 weeks of first contact (and before the 4-month follow-up time point). Calls were 10–20 min long and aimed to provide motivation and address any barriers to engagement.	Modules completed
Hadjistavropoulos et al.³⁷, Canada	Well-being Course. CBT. 5 lessons, 8 weeks. Unguided. Individual lessons focus on: (1) the cognitive behavioural model and symptom identification; (2) thought monitoring and challenging; (3) de-arousal strategies and pleasant activity scheduling; (4) graduated exposure; and (5) relapse prevention	Depression- and anxiety-related symptoms Post: 8 weeks Follow-up: 13.0 weeks	RCT	Email therapist support (standard) n = 91 Email therapist support (optional) n = 83	Adults self-reporting mild-mod depression or anxiety symptoms Standard: 38.2(11.4)yrs 82.4% Female Optional: 38.4(14.5)yrs 74.7% Female	NA	Trained therapists were instructed to: (1) show warmth and concern; (2) ask about patient's understanding of the material and need for help; (3) provide feedback on outcome measures; (4) highlight lesson content; (5) answer questions about the lesson and assist with use of skills; (6) reinforce progress and practice of skills; (7) manage any risks that presented and (8) clarify and remind patients of course instructions. Optional: no contact is offered unless the patient requests support.	1. % patients who accessed each lesson 2. No. emails sent to therapist, 3. Emails from therapist 4. Phone calls with therapist 5. App log-ins
Hadjistavropoulos et al.³⁸, Canada	Well-being Course. CBT. 5 lessons, 7 weeks. Unguided. Each lesson includes psychoeducational material in a slideshow format, patient stories, and downloadable lesson materials and assignments to facilitate skill acquisition.	Depression- and anxiety-related symptoms Post: 8 weeks Follow-up: 4, 16, 44 weeks	RCT	Speed of email response (one-day) (n = 233) Speed of email response (within one-week) (n = 216)	Adults college students (18 years and older). Self-reported depression or anxiety symptoms. 37.4(13.2)yrs 76% Female	NA	In all conditions, the assigned therapist would send an email to the patient on the designated day each week. In the 1BD condition, additional emails were sent within 1BD of receiving a patient email, were designed to be supportive, answer patient questions or respond to comments in patient emails	1. % patients who accessed each lesson 2. #log-ins to app
Hudson et al.³⁹, UK	Improving distress in dialysis (iDiD). 7 sessions, 12 weeks. Targets specific cognitive, emotional, and behavioural mechanisms associated with distress in hemodialysis. Encouraged to complete online sessions weekly with automated email reminders	Psychological distress from dialysis treatment Post: 12 weeks Follow-up: NA	RCT	Telephone support calls (n = 18)	HD patients recruited from a hospital. 49(11.4)yrs 44% Female	No strategy (n = 7)	30-min calls at weeks two, four, and six, all by a trained psychological well-being practitioner (PWP). Aimed at promoting engagement with the website and CBT skills	Sessions completed.
Levin et al.⁴⁰, USA	Online ACT 12 sessions. Unguided. Website sessions that included reflection questions and writing exercises as interactive features. Content was developed by clinicians trained in ACT. Transdiagnostic approach used to cover a variety of mental health issues.	Psychological distress Post: 6 weeks Follow-up: 4 weeks	RCT (secondary analysis)	Phone coaching + email prompts (n = 68)	College students aged 18 and above. Elevated levels of self-reported psychological distress 22.3(5.08)yrs mostly female 72.4% Female No group breakdown available.	Email prompts (n = 68)	All participants in active conditions received regular email reminders (weekly). Coaching was provided by two doctoral students with one year of training in basic counselling skills, and based on an established protocol. Weekly; 5–10 mins.	1. #sessions completed 2. % with 100% completion 3. % with at least 50% completion
Lillevoll et al.⁴¹, Norway	MoodGYM Unguided.	Depression-related symptoms Post: 6.5 weeks Follow-up: NA	RCT	Tailored email (n = 175) Standardised email (n = 176)	High school students. No between-group demographic data	No strategy (n = 175)	Standard: e-mails preceding each module providing a general introduction to the topic of each module. Tailored: based on data collected in the baseline survey on risk of depression, level of self-efficacy and self-esteem	Adherence was measured as number of modules with 25% progression or more, with modules 2–5 collapsed to one category to increase power
Mira et al.⁴², Spain	Smiling is Fun Transdiagnostic. Eight interactive modules, up to 12 weeks to complete. Unguided. Various components: motivation, psychoeducation, cognitive therapy, relapse prevention, behavioral activation component Self-help Internet-based.	Depression-related symptoms Post: 12 weeks Follow-up: 52 weeks	RCT	Automated phone support (n = 36) Automated + Human phone support (n = 44)	Adults aged 18–65years; recruited from community Elevated levels of self-reported depression Automated: 35.2(9.70)yrs 63.9% Female Automated + Human: 35.1(9.36)yrs 65.9% Female	NA	Automated: biweekly automated phone messages reminding and encouraging participants to continue with the programme. Human: weekly 2-min call by therapist to tell participants how they are doing with their progress in the programme. No clinical content.	Modules completed
Mohr et al.⁴³, USA	IntelliCare. Consists of 12 clinical apps, each targeting a specific strategy for improving symptoms of depression and anxiety, and a Hub app for consolidating user experience. 8 weeks. Unguided.	Depression- and anxiety-related symptoms Post: 8 weeks Follow-up: 26 weeks	RCT	Coaching only (C) (n = 76) Recommendations Only (R) (n = 75) Online coaching + recommendations (C + R) (n = 74)	Community sample recruited online. 18 years and older. Self-reported depression or anxiety C + R: 37.6(12.2)yrs 77% Female C only: 37.1(12.3)yrs 81% Female R only: 36.2 (11.5) yrs 72% Female	No strategy (n = 76)	Coaching: initial phone call, followed by 2–3 text messages/week to provide encouragement, support, and check progress. Recommendations: weekly phone notification providing recommendations to other IntelliCare apps, based on user's app use profile.	1. Time to last use (up to 6 months) 2. App use sessions during treatment 3. #App downloads
Proudfoot et al.⁴⁴, Australia	Online Bipolar Education Program (BEP) 8 module, 8 weeks. Unguided. Topics include: medications, psychological treatments, well-being plans, support networks	Symptoms of bipolar disorder Post: 8 weeks Follow-up: 26 weeks	RCT	Online peer support (n = 134)	Office workers aged 18–75. Age breakdown: <30: 28.9% 30–50: 42.4% >50: 28.7% No group-level demographic data	No strategy (n = 139)	Online coaching provided via email by people with Lived Experience of Bipolar Disorder. Aims of coaching were to help users apply skills in their lives, and answer any questions they have in managing their symptoms.	Completion of at least 4 of 8 module workbooks.
Renfrew et al.⁴⁵, Australia	eLMS and a mobile app called “MyWellness.” Theory of planned behavior (TPB) 10 modules, 10 weeks. Unguided. Interdisciplinary intervention covering a range of evidence-based strategies for enhancing mental well-being.	General mental well-being Post: 12 weeks Follow-up: NA	RCT	Emails only (n = 157) Emails + Text (n = 163) Emails + Videoconferencing (n = 138)	Adults aged 18–81 years. Non-clinical sample.	NA	Participants received a weekly email on the day before the next session commencing. The email included a link to a 20 to 25 s video by the presenter, inviting them to engage with the next presentation. S + pSMS group received automated emails plus SMS messages sent thrice weekly for the first 3 weeks, and twice weekly for the remaining 7 weeks. S + VCS group were invited to attend a synchronous, videoconference session using the app “Zoom.” A weekly timetable provided 9 different timeslots to choose from.	1. # videos viewed 2. # challenge activities completed
Santucci et al.⁴⁶, USA	Beating the Blues (BtB). CBT. 8 sessions, 8 weeks. Unguided Web-based, imparting cognitive-behavioral strategies for the treatment of anxiety and depression.	Depression & anxiety symptoms Post: 9 weeks Follow-up: 4 weeks	RCT	Email reminders (n = 21)	College students who attended a university behavioural medicine clinic. Elevated levels of self-reported depression 22.9(4.2)yrs 75% Female No between-group demographic data reported.	No strategy (n = 22)	Weekly emails from research team reminding them to complete their BtB session for the week.	# sessions completed.
Simon et al.⁴⁷, USA	MyRecoveryPlan 8 modules, 3 weeks. Unguided. Modules covering education, recovery plan, self-monitoring, social networking and consumer activation.	Bipolar Disorder Post: NA Follow-up: NA	RCT	Online peer coaching (n = 64)	Adults with bipolar disorder. No age data 72% Female No between-group demographic data	No strategy (n = 54)	Peer specialists were people with lived experience in bipolar disorder and completed specialised training Participants in the coaching group were encouraged to send messages to coaches seeking additional information or support.	Access and use of specific components of MyRecoveryPlan
Titov et al.⁴⁸, Australia	cCBT. 6 lessons, 8 weeks. Unguided. Summary/homework assignment for each lesson, automatic emails and fortnightly SMS messages	Social phobia Post: 8 weeks Follow-up: NA	RCT	Telephone prompts (n = 84)	Adults meeting DSM-IV criteria for social phobia. M = 41.2 years 52% Female (no group breakdown)	No strategy (n = 84)	Weekly calls by a research assistant, at a time specified by the participant, when they were commended and encouraged to persevere but no clinical advice was offered.	1. Adherence: complete all 6 lessons within 8 weeks 2. Mean lessons completed
Titov et al.⁴⁹, Australia	Well-being Course. CBT. 5 lessons, 8 weeks. Unguided. Each lesson includes psychoeducational material in a slideshow format, patient stories, and downloadable lesson materials and assignments to facilitate skill acquisition.	Depression & anxiety Post: 8 weeks Follow-up: NA	RCT	Email prompts (n = 100)	Adults aged 18 and above with self-reported depression, GAD, social phobia, or panic disorder. Adults 40.3(10.1)yrs 77% Female	No strategy (n = 106)	All participants received email at the start. Thereafter, the Email group received at least 2 emails/week. Emails were triggered upon completion of a lesson, or non-completion of a lesson 7 days after its release.	% completed all 5 online lessons