The first Aim of this proposal is to determine the relationship between social determinants of health (SDoH) and treatment selection/receipt in jail, and the second Aim is to use that information in a propensity score weighted analysis to measure the effectiveness of the program and provide methodological guidance to other research in the field. This proposal builds on previously funded JCOIN work by explicitly considering how SDoH and other factors drive treatment assignment in the pilot program and how this could confound the relationship of treatment assignment and outcomes. We will use data from 7500 individuals incarcerated in Massachusetts in a jail offering MOUD, and assess how the choice of MOUD in jail is associated with uptake of MOUD and occurrence of overdose post-release with a focus on the role of SDoH and methodological implications for other work in the field. This proposal addresses a critical barrier to studying interventions and informing future programs and can be employed by researchers at JCOIN and elsewhere now. J-RIG funding will allow us to deliver an innovative methodological toolkit, through a comparison of methods, to guide current and future analysis both within JCOIN and in other work. Specifically examining how SDoH drive treatment assignment and outcomes simultaneously – and how to address that – is invaluable for informing future interventions and research aimed at improving health outcomes and equity for incarcerated individuals.