Table 1.

Theory-based recommendations for the design of digital health interventions.

Design feature	Recommendation
Tailoring	• Tailored content should: (a) contain explicit self-referent cues or personally relevant information (e.g. user's name); (b) acknowledge potential counterarguments before seeking to persuade, change beliefs or introduce new knowledge.
Social support and interaction	• Social support features are useful when: (a) users lack sufficient peer support outside of the intervention context; (b) they can offer an acceptable and realistic substitute for face-to-face interaction; (c) users are managing a health problem that requires a change in identity or disclosing experiences of stigmatised conditions; (d) they provide opportunities for users to provide as well as receive peer support; (e) frequency and type of support provided can adapt to users' changing support needs; (f) they can be adequately moderated or facilitated.
Self-management	• Goals are more likely to motivate behavioural change if they are: (a) achievable; (b) sufficiently challenging; (c) specific; (d) specify proximal changes to behaviour that are tied to a distal aim; (e) learning orientated; (f) fit with already valued goals or self-conceptions. • Provide rationale for goal setting and guidance through the process. • Allow users to choose from a pre-defined list of goals in order to support autonomy and ensure that appropriate goals are set. • Tailored feedback on goal progress should: (a) strengthen self-efficacy beliefs; (b) be positively framed (i.e. emphasise the immediate benefits of positive change, rather than the negative consequences of not changing behaviour); (c) demonstrate a clear link between users' (current and future) behaviour and health-related outcomes; (d) adapt to changing needs and experience of the user.
Information architecture	• Target population should be consulted during intervention development in order to ascertain their perceived role and expected level of involvement in different aspects of intervention delivery (e.g. access to informational content, choice in goal-setting and self-monitoring, frequency of contact to and from the intervention). • Where appropriate, users should be afforded autonomy and control over intervention usage (e.g. navigational choices, selection and application of behaviour change techniques).
General	• Users should be invited to provide feedback to the intervention, research team, or health professionals. • The intervention should provide a meaningful rationale for why behaviour change is important and the specific information and advice that is provided. This rationale should acknowledge users' concerns (e.g. that behaviour change is not necessarily easy or enjoyable).