BACKGROUND Impulsivity is a hallmark feature of self-regulation failures that lead to poor health decisions and outcomes, making understanding and treating impulsivity one of the most important constructs to tackle in building a culture of health. Despite a large literature base, impulsivity measurement remains difficult due to the multi-dimensional nature of the construct and limited methods of assessment. Mobile devices and the rise of mobile health changed our ability to assess and intervene

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... with individuals remotely, providing an avenue for ambulatory diagnostic testing and interventions. OBJECTIVE Develop and validate a mobile health (mHealth) diagnostic and monitoring app of impulsivity called the Digital Marshmallow Test (DMT) using both the Apple and Android platforms for widespread dissemination to researchers, clinicians, and the general public. METHODS Digital Marshmallow Test (DMT) was developed based on Apple's ResearchKit (iOS) and ResearchStack (Android) open-source frameworks for developing health research study apps. DMT app consists of three main modules: basic and smart self-report, ecological momentary assessments, and active behavioral and cognitive tasks. We conducted a 21-days study (N=116) to validate the novel measures of the DMT app. RESULTS We used semantic differential scale to develop a self-report trait and state measures of impulsivity as part of the DMT app. We identify three factors (inefficient, thrill-seeking, and intentional) that correlated highly with established measures of impulsivity traits. We further leveraged momentary semantic differential questions to examine intra-individual variability, the effect of daily life, and the contextual effect of mood on state impulsivity and related constructs. We also validated novel mobile versions of behavioral and cognitive tasks. Our results indicate high validity of the mBART task (Balloon Analogue Risk Task), moderate validity of the mGNG task (Go-no-go), and low validity of the mDD task (Delayed Discounting). We discuss the design implications of these results to mobile health research. CONCLUSIONS The study demonstrated the potential for assessing trait and state impulsivity during everyday life using the Digital Marshmallow Test (DMT) mobile app. DMT app can be further used to enhance our understanding of impulsivity and related constructs as well as to provide a promising avenue for digital interventions. CLINICALTRIAL ClinicalTrials.gov NCT03006653