Defining and reporting treatment dropout in blended therapy for mental health: scoping review and analysis.

Evidence suggests that blended therapy combining face-to-face psychotherapy with digital components may reduce treatment dropout, yet definitions of dropout vary widely. This variability is particularly pronounced in blended therapy, where dropout may involve discontinuation of in-person sessions, disengagement from digital components, or both. This study aimed to identify operational definitions of treatment dropout in blended therapy and to examine how different definitions influence dropout rates, treatment outcomes, and usage patterns. A scoping review identified 14 studies reporting operational definitions of dropout. Five synthesized definitions were applied to data from a large blended therapy trial, revealing variation in dropout rates and their associations with depressive symptoms, anxiety, and life satisfaction. Cluster analysis further identified distinct digital usage patterns. These findings highlight the need for transparent and differentiated reporting of dropout definitions in blended therapy research to improve comparability and interpretation across studies.