Project Summary/Abstract. Hypertension (high blood pressure) affects 1 in 3 of the over 90 million people currently enrolled in Medicaid, and is a leading cause of cardiovascular disease and stroke in the U.S. While multiple effective anti-hypertensive (AH) drugs are widely available in the U.S., they require high (≥80%) life- long medication adherence to successfully counter cardiovascular morbidity and mortality. Unfortunately, AH medication adherence is lowest among Medicaid enrollees compared to other insured populations, and nonadherence is a major barrier to controlled blood pressure. The mechanisms of present bias and habit strength have been shown to maintain behavior change in several settings, but have not been tested for maintaining high AH medication adherence. Incentives are effective for improving medication adherence in the short term, and may reduce present bias by helping people better internalize the future benefits of their actions, which in turn could maintain AH medication adherence. Therefore, we propose to partner with the widely-used, commercial Wellth smartphone app, where app users can earn incentives for sending photographic evidence of their daily pill taking. After withdrawing the Wellth-delivered incentives, we will measure adherence maintenance. Habitual pill-taking is another key strategy for maintaining behavior change, since habits performed in response to the same contextual cue for roughly four months are executed with high habit strength, i.e., are performed with little or no cognitive effort. Existing habit formation interventions have had difficulty effectively supporting participants, but behavioral economics suggests that providing small incentives for cueing the new behavior can effectively support habit formation. Thus, this study proposes to also adapt the Wellth app to reward cued AH pill taking. In a Stage III, 24-month 3-arm real-world efficacy trial, hypertensive adults with low (<80%) adherence from Arizona Complete Health’s Medicaid plan (n=600; 200 per group) will be randomly assigned to: 1) ‘Control’ group; 2) ‘Wellth Only’ that will receive daily incentives for submitting a picture of their AH pill taking; or 3) ‘Wellth+Cue’ that will be asked to describe the cue that will trigger their AH pill taking and send a second picture of the contextual cue, such as a coffee mug. A 4-month intervention will be followed by a 20-month post-intervention period to measure maintenance. The Primary Outcomes are mean AH medication adherence (days covered measured via Medicaid claims) and blood pressure (via at-home readings at baseline and months 4, 8, 12, and 24). Secondary Outcomes are healthcare utilization (emergency and inpatient visits) and the costs incurred by Medicaid (via claims data). After the study ends, interviews with stakeholders and participants (using a positive/negative deviance approach) will ask about potential implementation barriers to inform intervention refinements and cultural adaptat...