PROJECT SUMMARY/ABSTRACT This proposal aims to determine whether an adjunctive Mindfulness-Based Relapse Prevention (MBRP) treatment program improves medication adherence and reduces drug-use among opioid use disorder (OUD) patients receiving extended-release naltrexone (XR-NTX). The broad long-term objectives of this project are to investigate how integrative pharmacological and behavioral treatments improve OUD treatment outcomes. XR-NTX is an evidenced based medication-assisted treatment (MAT) for OUD that has demonstrated utility in reducing opioid craving and rates of relapse and overdose deaths. However, a large portion of OUD patients demonstrate poor adherence to this medication and subsequently face increased vulnerability to future drug- use. Limited research has examined how behavioral treatments can increase MAT adherence. Mindfulness (i.e., present-centered nonjudgmental awareness), associates with self-care and addiction severity among with substance use disorders (SUD). MBRP is an evidenced-based behavioral group intervention that has demonstrated efficacy in reducing drug-use among patients in recovery from SUD. Emerging research suggests that combining MBRP into MAT for OUD may improve medication adherence and reduce drug-use. The primary study aim is to determine whether MBRP, compared to treatment-as-usual (TAU), delivered to OUD patients receiving XR-NTX through enrollment in a residential addiction treatment facility, results in improved MAT adherence and reduced drug-use following residential discharge. As MBRP is understood to improve self-care and mental health via increases in mindfulness and distress tolerance, the second study aim will test whether these mechanisms of change mediate XR-NTX adherence and drug-use outcomes. As prior trauma exposure is observed to undermine treatment efforts for SUDs a third exploratory study aim will determine the extent to which baseline trauma exposure and posttraumatic stress undermine XR-NTX adherence and drug-use. Expected outcomes are that MBRP participants will demonstrate (1) increased XR- NTX adherence and reduced drug-use monitored across three-months post-treatment, (2) that increased mindfulness and distress tolerance will mediate these outcomes, and (3) that prior trauma exposure and posttraumatic stress will moderate outcomes for TAU participants, but not for MBRP participants. Executing this project will provide enriching research opportunities for student research assistants. Providing students with systematic training and opportunities for exposure to research activities is fundamental to the study PI’s career aspirations and is an essential component to the successful execution of this research proposal. Findings from this research proposal will contribute to endeavor to improve addiction treatment efforts, will provide substantive opportunities for student researchers, and will provide foundational support for the PI’s pursuit of additional R01 funding prior to the conc...