The definition and measurement of engagement and adherence for digital mental health interventions: An umbrella review

Digital Mental Health Interventions (DMHIs) are scalable and accessible, but low engagement and adherence limit their effectiveness. Varying definitions and measures of engagement and adherence hinder effective evaluation and comparison. This umbrella review synthesised 61 systematic reviews, meta-analyses, and scoping reviews, which focused on DMHIs and provided a definition or measurement of engagement and/or adherence. Inclusion and exclusion were guided by PICOS, with record counts reported in the PRISMA flowchart. Results showed that adherence and engagement were often undefined. When defined, engagement was most often combined with adherence or described as extent of programme usage, with completion metrics and usage metrics being the two most common measurements. When defined, adherence was most often described as programme/module/session completion or combined with engagement, with completion metrics or a combination of completion and usage metrics being the two most common measurements. Factors influencing engagement and adherence clustered into three themes: (i) participant level factors (e.g. demographic variables), (ii) technology level factors (e.g. privacy concerns), and (iii) programme level factors (e.g. perceived usefulness of the DMHI). Results are discussed in terms of how engagement and adherence to DMHIs are defined, measured, and promoted, highlighting priorities, challenges and recommended practices.