Postpartum Recovery from Opioid Use Disorder through Daily Acceptance and Commitment Therapy (PROUD2ACT) - PROJECT SUMMARY/ABSTRACT The postpartum period for up to one year after childbirth is a vulnerable time for individuals recovering from opioid use disorder (OUD). Postpartum people with OUD commonly experience psychosocial stressors, such as mental health problems and child welfare involvement, that can destabilize recovery, increasing risk for medication treatment for OUD cessation, return to substance use, and overdose. Despite pregnancy- associated overdose death rates peaking at 7-12 months after delivery, interventions designed to help people with OUD to maintain stability and continuity in addiction treatment and recovery after transitioning to the postpartum period are lacking. Mobile health (mHealth) interventions are ideally suited for this purpose given that they can provide personalized, real-time support in natural environments. The goal of the proposed research is to develop a mHealth intervention that provides psychosocial and self-management support to postpartum individuals recovering from OUD. Grounded in the principles of Acceptance and Commitment Therapy (ACT), the intervention will be iteratively developed and refined with input from members of the target population and incorporate a just-in-time adaptive intervention (JITAI) component that delivers real-time notifications to increase user engagement with its content. The following aims are proposed: (1) develop a mobile ACT intervention specific to postpartum individuals recovering from OUD using a stakeholder-engaged approach and (2) evaluate the feasibility and acceptability of conducting a micro-randomized trial (MRT) with postpartum individuals recovering from OUD. This research is part of a larger comprehensive training plan that will enable Dr. Charron to become an independent investigator focused on the development and evaluation of novel mHealth interventions that provide real-time addiction treatment and recovery support to pregnant and postpartum individuals with substance use disorder (SUD). Proposed training activities are in four areas: (1) JITAI and MRT design, (2) adapting and optimizing behavioral interventions, (3) behavioral treatments for SUD, and (4) professional development. Expertise of a strong mentoring team, combined with the rich training environment of University of Oklahoma Health Sciences, will ensure the success of this project. Completion of the proposed K01 award will provide preliminary data and a training foundation to support a future R01 proposal to conduct a MRT to optimize the JITAI component of the mHealth intervention.