Capturing Mechanisms of Change in Behavioral Activation using Modern Intensive Longitudinal Assessment Methods: Protocol for A Scoping Review

Objective: The objective of this scoping review is to identify research that utilizes modern intensive longitudinal assessment methods (e.g., Ecological Momentary Assessment [EMA]; Experience Sampling [ESM], Daily Diary) to study the mechanisms of change in behavioral activation. Introduction: Behavioral activation (BA) is an efficient and accessible transdiagnostic therapy that has demonstrated considerable effectiveness across populations, settings, and delivery formats. Despite decades of research on BA, its underlying mechanisms remain understudied, partly due to the use of inadequate methodologies. Modern intensive longitudinal assessment methods, like ecological momentary assessment administered via a smartphone, are ideally suited to capturing mechanisms of change in therapy because they facilitate examination of dynamic within-person processes across large samples. To date, such research is fairly limited and has never been summarized.Inclusion criteria: We will include peer-reviewed empirical articles on clinical trials of BA that examine mechanisms of change in the context of treatment captured with modern intensive assessment methods. No restrictions will be placed on the sample or treatment setting, with the exception that small N studies (N < 5) will be excluded. Clinical trials of treatments that include BA alongside other interventions (e.g., cognitive restructuring) will be excluded.Methods: The search strategy will aim to locate published studies from database inception up to October 14, 2025. A comprehensive search of PubMed, PsycInfo, Embase, and Web of Science will be undertaken by independent reviewers to identify peer-reviewed articles on the topic. Data extracted from eligible studies will include information about the article, sample characteristics, intervention details, mechanism assessment details, and main findings regarding the mechanisms.