Assessment of study quality

Fifteen out of the nineteen studies were rated as high quality, with a score of 9 or above [12, 33,34,35,36,37,38,39,40,41,42,43,44,45,46]. The rest of the studies were rated as moderate quality, scoring either 7 or 8 [14, 47,48,49]. None of the included studies were rated as low quality (scoring 6 or below). Scores on individual items for all included studies can be found in Table 1. In all of the studies, there was a clear statement of aims, and the methods were deemed appropriate to address these aims. For five of the studies, the method used to analyse the data was stated, however a more detailed reporting of the steps used to analyse the qualitative data was not clearly stated [14, 42, 43, 47, 49]. The item that was scored most poorly across the included studies was in relation to reflexivity and bias. Only seven out of the nineteen studies had a clear reflexivity statement or explanation of the researchers’ relationship with the participants [12, 33, 34, 39, 42, 44, 45].

Table 1 Quality assessment scores of included studiesThematic synthesis

After screening 407 records that were identified in the search, 19 studies were found to meet the inclusion criteria for the thematic synthesis (see Fig. 1).The number of participants across the studies ranged from 6 to 95 (M = 22.5). The mean ages of the participants ranged from 20 to 55yrs across the studies. In total, 54.1% of the participants across all of the studies were male, 45.7% were female, and 0.2% were transgender. The ethnicity of participants was not reported in 6 out of the 15 studies. In studies that did report on ethnicity, between 42.1 and 100% of participants were White. 10 out of 15 studies used a mixed-method design, with the remaining four employing only qualitative methods. Further information on the included studies are detailed in Table 2. The synthesis resulted in six overarching themes and sixteen sub-themes (Table 2). The six themes were: (1) Content of digital intervention, (2) relationship with technology, (3) accessibility, (4) awareness and management of mental health, (5) enhancing communication and relationships, and (6) opportunity for reflection. A thematic map describing the themes and sub-themes can be found in Fig. 2 (Table 3).

Table 2 Summary of studies included in reviewFig. 2

Thematic map of themes and sub-themes

(1) Content of digital intervention

This theme relates to specific features of the digital interventions that participants found helpful and unhelpful, and also suggestions on how the content of the digital intervention could be improved. This theme is comprised of three subthemes: (I) tailoring to specific needs, (II) views on notifications/reminders, and (III) range of content. For participants, having interventions that felt meaningful to their experiences as well as feeling they can trust the information within interventions are important for motivation and longevity of use. Notifications received through interventions can be helpful, encouraging engagement when it fits within daily routines and other activities. When notifications are inaccurate, causing additional stress, they can reduce people’s willingness or motivation to use the intervention. This may lead to participants ignoring notifications which could impact on long term usage or effectiveness of interventions. When tasks feel mundane or participants no longer feel they are able to learn new skills, interest in or motivation to use interventions may decrease. There, however, needs to be a balance between feeling challenged with learning new skills, however not having content that is too challenging which could cause people to feel overwhelmed or deskilled. Providing solution focused interventions can help participants to feel good and think more positively about the intervention, ensuring that it feels like a positive addition to their lives.

(I)

Tailoring to specific needs

Being able to customise and tailor interventions to individual needs was reported as an important feature. This included being able to see visual representations of their own experiences, personalising reminders, and having the option to write qualitative feedback [33, 35, 40, 43, 46,47,48]. ‘’I would've changed my prompts to check in with my sleep’’ [p.6, 47]. Participants reported difficulty using interventions in instances where the content was hard for them to relate to, or when there were concerns related to the accuracy of data recorded in the intervention [36, 37, 43, 47]. ‘’Hard to relate to the content, mostly for teenagers (had to put examples to my own context)’’ [Participant 6, Suppl material, 48].

(II)

Views on notifications/reminders

Notifications and reminders were consistently reported as helping participants to complete tasks such as remembering to take medication, or feeling supported when receiving positive messages [12, 33,34,35,36, 45, 47]. ‘’most participants in both groups commented on the overall positive tone of the apps and how this was a necessary attribute to maintain their engagement over time’’ [p. 9, 36]. Negative views associated with notifications and reminders included receiving too many prompts, timing inaccuracies, and receiving false alarms on potential relapses [14, 33, 39, 47]. ‘’Overall, 5 participants commented on how they would have concerns over false alarms—for example, whether sleeping poorly in the absence of deterioration in symptoms would trigger a response’’ [p. 8, 39].

(III)

Range of content

The content range of interventions were reported to be too limited, with participants expressing a need for the content to be broader and to have more options. This was especially the case after a sustained period of continued use, which could be seen as repetitive over time [33, 39, 44,45,46,47,48]. ‘’..I found content on the actual app was too limited..” [Participant 128, p.1078, 14]. Participants also commented on positive aspects of the intervention content including finding it enjoyable answering questions, the overall supportive tone, and having more solution-focused content [34, 38, 44, 47]. ‘’Audrey identified the positive environment on Horyzons as an important element of her high usage level. She did not want to spend time at a place where “the people are all negative” [p. 7, 44].

(2) Relationship with technology

This second theme is comprised of three subthemes which include participants’ views on technology and their previous experiences of using technology. These were (I) experience of technology, (II) concerns about technology, and (III) technical issues. Existing experience or views about technology could impact on people’s initial willingness or ability to use interventions, however these views can be altered through support from others and with increased familiarity. Having a lack of experience using technology could increase feelings of disempowerment, disconnection and confidence. This could mean that participants do not experience the full benefits that such technology could offer. Technology could impact or interact with pre-existing concerns about monitoring and therefore impact on paranoia. The way in which tracking or monitoring is perceived could impact on how attitudes towards interventions which could be negative or create a sense of safety from knowing others may be supporting from afar.

(I)

Experience of technology

A lack of experience using technology was cited as a reason why participants found it difficult to engage with an intervention, however for some, this improved over time [33,34,35, 46]. ‘’..the rest of us never had a smartphone. I think a class on how to use it would be helpful’’ [Participant 6, p.10, 40]. For others, this lack of experience could restrict their interaction with the intervention and affect their motivation to use it, or in some cases, result in them discontinuing their use [12, 34, 35, 38, 43]. ‘’Lack of smartphone experience was a barrier in some cases, with 1 participant accidentally deleting the app from the phone and 2 others commenting that their lack of smartphone experience prevented them from accessing the app's extra features’’ [p. 17, 34].

Receiving training and/or support with using the intervention was, in some instances, helpful and enabled people to continue using it even after experiencing initial difficulties. However, limited access to the internet could cause some participants to continue experiencing difficulties in engaging [33, 40, 43, 45]. ‘’watching the videos at home supported the information to “sink in” for Viv. Participants who had no or limited Internet access at home due to reception, accommodation, or financial difficulties, did not have this opportunity’’ [p. 8, 45].

(II)

Concerns about technology

Concerns about technology, specifically with privacy and access to data were raised across a number of studies [33,34,35, 37,38,39, 44]. Some participants reported experiencing feelings of paranoia about being monitored or concerns that others would be able to see the content of the intervention whilst using it in public [12, 34, 39, 46]. ‘’It's difficult for me … yeah I always felt a bit of conscious somebody might be coming along and looking over your shoulder'' [Participant S8, p. 690, 12]. For others, being monitored or tracked by therapists was seen as a positive, leading them to feel safe and supported [33, 43]. ‘’participants were positive about the therapist being able to track how they were doi