Date of Award

January 2022

Document Type


Degree Name

Medical Doctor (MD)



First Advisor

Declan T. Barry


Overdose, most commonly from opioids, is the leading cause of death among people experiencing homelessness. Medication for opioid use disorder is an evidence-based treatment that combines pharmacotherapy with an opioid agonist or antagonist with counseling and reduces morbidity, opioid craving and use, infectious disease risk, and overdose-related and all-cause mortality. However, only a minority of patients with opioid use disorder are enrolled in medication for opioid use disorder, and those experiencing homelessness are significantly less likely to engage in this life-saving treatment than their housed counterparts. Few studies have compared differences in patient characteristics or retention based on housing status in outpatient medication for opioid use disorder treatment. The present thesis presents three sequential studies that directly compare housed and unhoused patients and their outcomes in medication for opioid use disorder. The first study was a cross-sectional study to compare patient demographic, diagnosis-related, and treatment-related characteristics in an outpatient, low-barrier methadone program. We hypothesized that homelessness would be associated with higher levels of depressive symptoms. The second was a retrospective cohort study that further investigated patient demographic and clinical characteristics and the potential impact of these variables and housing status on treatment retention. We hypothesized that compared to patients who were housed at treatment enrollment, patients experiencing homelessness would have higher rates of chronic pain, higher levels of overall psychiatric distress, and lower levels of retention. The third used a large national database of all publicly funded substance use treatment episodes in the United States from 2016-2018 to investigate whether the differences based on housing status identified in the first two studies were observed at the national level among medication for opioid use disorder treatment programs that offer methadone, buprenorphine, or naltrexone, many of which do not use a low-barrier to treatment entry approach. We hypothesized that the association between housing status and retention would remain after accounting for other covariates. In the first study, we found that patients experiencing homelessness were significantly more likely to be male and to report more depressive symptoms. In the second study, we found that homelessness was significantly associated with increased social isolation, chronic pain, trauma, psychiatric distress, and one-year treatment discontinuation. In the final study, the patients reporting homelessness at treatment entry had numerous significant differences in demographic, social, and clinical characteristics from those with stable housing and experiencing homelessness was significantly and negatively associated with staying in outpatient MOUD treatment for longer than 180 days or completing treatment after accounting for covariates. Addressing the clinical vulnerabilities and reduced retention faced by patients experiencing homelessness enrolling in outpatient medication for opioid use disorder is an urgent priority.


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