Abstract
OBJECTIVE: Eating disorders (EDs) contribute considerably to the global burden of disease. However, most affected individuals do not receive treatment. Mobile apps present an enormous opportunity to increase access to mental healthcare services. This study examined whether the degree of usage of a self-help app for EDs mediated the app's effects on the clinical response by individuals with EDs. METHOD: App usage measures included the total number of cognitive-behavioral meal logs, total number of days spent using the app, and the last day the app was used during the study period. Mediation analysis was performed using the MacArthur framework. RESULTS: All usage variables met the analytic requirements for testing mediation (group means (sd) for app and standard app, respectively: logs = 74 (108) vs. 51.4 (88.1), days spent = 14.3 (17.5) vs. 10.6 (15.0), p-values from Wilcox rank sum tests p < .01). Regression coefficients indicated mediation effects. The mediation effects demonstrated support that increased engagement (as measured by logs and time spent on the app) was related to an increased likelihood of achieving a significant clinical change by the end of the trial. DISCUSSION: Greater and longer engagement in an ED app mediates its efficacy in terms of ED remission.