Assessing Patient Adherence to and Engagement With Digital Interventions for Depression in Clinical Trials: Systematic Literature Review

Abstract

Background: New approaches to the treatment of depression are necessary for patients who do not respond to current treatments or lack access to them because of barriers such as cost, stigma, and provider shortage. Digital interventions for depression are promising; however, low patient engagement could limit their effectiveness.

Objective: This systematic literature review (SLR) assessed how participant adherence to and engagement with digital interventions for depression have been measured in the published literature, what levels of adherence and engagement have been reported, and whether higher adherence and increased engagement are linked to increased efficacy.

Methods: We focused on a participant population of adults (aged ≥18 years) with depression or major depressive disorder as the primary diagnosis and included clinical trials, feasibility studies, and pilot studies of digital interventions for treating depression, such as digital therapeutics. We screened 756 unique records from Ovid MEDLINE, Embase, and Cochrane published between January 1, 2000, and April 15, 2022; extracted data from and appraised the 94 studies meeting the inclusion criteria; and performed a primarily descriptive analysis. Otsuka Pharmaceutical Development & Commercialization, Inc (Princeton, New Jersey, United States) funded this study.

Results: This SLR encompassed results from 20,111 participants in studies using 47 unique web-based interventions (an additional 10 web-based interventions were not described by name), 15 mobile app interventions, 5 app-based interventions that are also accessible via the web, and 1 CD-ROM. Adherence was most often measured as the percentage of participants who completed all available modules. Less than half (44.2%) of the participants completed all the modules; however, the average dose received was 60.7% of the available modules. Although engagement with digital interventions was measured differently in different studies, it was most commonly measured as the number of modules completed, the mean of which was 6.4 (means ranged from 1.0 to 19.7) modules. The mean amount of time participants engaged with the interventions was 3.9 (means ranged from 0.7 to 8.4) hours. Most studies of web-based (34/45, 76%) and app-based (8/9, 89%) interventions found that the intervention group had substantially greater improvement for at least 1 outcome than the control group (eg, care as usual, waitlist, or active control). Of the 14 studies that investigated the relationship between engagement and efficacy, 9 (64%) found that increased engagement with digital interventions was significantly associated with improved participant outcomes. The limitations of this SLR include publication bias, which may overstate engagement and efficacy, and low participant diversity, which reduces the generalizability.

Conclusions: Patient adherence to and engagement with digital interventions for depression have been reported in the literature using various metrics. Arriving at more standardized ways of reporting adherence and engagement would enable more effective comparisons across different digital interventions, studies, and populations.

Keywords: adherence; depression; digital health; digital interventions; digital therapeutics; engagement; major depressive disorder; mobile health; mobile phone; systematic literature review.

Figure 1

PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) diagram. MDD: major depressive disorder.

Figure 2

Engagement and adherence outcomes for commonly reported metrics. This graph displays the average values for the most reported engagement and adherence metrics, calculated from the means reported by the studies. The dose-received metric was calculated from the studies (38/94, 40%) that reported the number of modules used and the number of available modules (by dividing the former by the latter). For each metric, the highest and lowest means reported are also displayed, as well as the number of studies from which the metric was calculated (note: some studies reported means from multiple digital interventions, accounted for in the footnotes). ^a42 values from 38 studies, ^b37 values from 33 studies, ^c51 values from 43 studies, ^d20 values from 19 studies, ^e12 values from 9 studies, ^f7 values from 5 studies.

Figure 3

Summary of efficacy and engagement across the studies based on access to psychotherapy, intervention delivery with support, and mode of digital delivery. (A) Efficacy based on whether or not participants had access to psychotherapy. (B) Participant adherence and engagement based on whether access to psychotherapy was permitted. (C) Efficacy based on whether or not the digital interventions were delivered with support. (D) Participant adherence and engagement based on whether or not the interventions were delivered with support. (E) Efficacy based on whether the interventions were delivered via the web or via apps (the latter included interventions that were exclusively app-based and those that were app-based but could also be accessed via the web). (F) Participant adherence and engagement based on whether the interventions were delivered via the web or via apps. ^aEfficacy refers to at least 1 outcome in which the digital intervention group experienced significantly greater improvement than the control group, ^b30 values from 24 studies, ^c12 values from 11 studies, ^d21 values from 17 studies, ^e10 values from 9 studies, ^f31 values for 27 studies, ^g39 values from 33 studies, ^h3 values from 2 studies, ⁱ39 values from 32 studies, ^j9 values from 8 studies.