Summary of key findings of RCTs for DMHIs.

Digital mental health interventions (DMHIs) are a potential scalable solution to improve access to psychological support and therapies. DMHIs vary in terms of their features such as delivery systems (Websites or Apps) and function (information, monitoring, decision support or therapy) that are sensitive to the needs and preferences of users. A decision aid is warranted to empower people to make an informed preference-based choice of DMHIs. We conducted a review of features of DMHIs to embed within a patient decision aid to support shared decision-making. DMHIs, with evidence of availability in the United Kingdom (UK) at the time of the review, were identified from interactive meetings with a multi-disciplinary steering group, an online survey and interviews with adults with lived experience of using DMHIs in the UK. Eligible DMHIs targeted users age ≥16 years with a mental health condition(s), delivered through a digital system. A previous classification system for DMHIs was extended to eight dimensions (Target population; System; Function; Time; Facilitation; Duration and Intensity; and Research Evidence) to guide data extraction and synthesis of findings. Twenty four DMHIs were included in the review. More than half (n = 13, 54%) targeted people living with low mood, anxiety or depression and were primarily delivered via systems such as Apps or websites (or both). Most DMHIs offered one-way transmission of information (n = 21, 88%). Ten (42%) also had two-way communication (e.g., with a healthcare provider). Eighteen (75%) had a function of therapy, with seven and five DMHIs providing monitoring and decision support functions respectively. Most DMHIs were capable of being self-guided (n = 18,75%). Cost and access were primarily free, with some free via referral from the UK NHS or through corporate subscription for employees (n = 11). Eight (33%) DMHIs had evidence of effectiveness from randomised controlled trials. Six statements were developed to elicit user preferences on features of DMHIs: Target Population; Function; Time and Facilitation; System; Cost and Access; and Research Evidence. Preference elicitation statements have been embedded into a prototype decision aid for DMHIs, which will be subjected to acceptability and usability testing.