Table 1.

Challenges for developing and evaluating digital interventions targeting behavior change.

Topics	Challenges
Pace and efficiency	Rapid technological change and iterative development cycles make it necessary to continually update and adapt interventions.
	Existing development and evaluation cycles are slow and unsuited to dynamic systems and rapidly changing contexts.
	Efficient, continuing relationships between academics and intervention developers are needed for implementation, continued development, and evaluation.
Engagement	Engagement with digital interventions is often too limited to support behavior change.
	Engagement is multidimensional and cannot be evaluated simply by DBCIa usage.
	Engagement with DBCIs may be unequal between different groups and at risk of reinforcing disparities or inequalities.
Theory	Often, there is a lack of clarity around the mechanisms through which DBCIs have their effect.
	Methods of characterizing intervention components, mode of delivery, and contexts that characterize their essential features are required but limited.
Evaluation of effectiveness	Controlling the testing environment is made problematic by the ready availability of alternative interventions.
	It is difficult to specify comparator interventions or control conditions that allow meaningful evaluation of the intervention of interest.
	Better methods for structuring and analyzing very large, dynamic, and heterogeneous data sets are needed.
	Reach and engagement can be low.
	The complex multi-component nature of interventions requires an iterative design and testing cycle.
Evaluation of cost-effectiveness	There is a lack of techniques for economic and cost-effectiveness evaluation across the digital development, deployment, and delivery cycle.
	Funding mechanisms are not aligned with the digital model of development, implementation, iterative improvement, and evaluation.
Regulation, ethics, and information governance	There are competing commercial and ethical demands on data ownership and intellectual property.
	There are emerging and different standards around ethical or institutional review in the biomedical, psychological, and digital development communities.
	There are uncertain quality standards and regulatory processes for digital interventions (with standards either in development or inappropriately adapted from other contexts).

^aDBCI: Digital behavior change interventions.