(55) Who Gets Treatment? Substance Use Disorder Treatment Enrollment after Traumatic Injury

Background & Introduction: Substance use disorder (SUD) can be both a risk factor and a result of unstable housing status. (1) People experiencing homelessness (PEH) are chronically understudied in medical literature and are more likely to experience traumatic injury, SUD, and frequent emergency department usage when compared to people who are housed.(2-4) Research exploring SUD treatment engagement among PEH is sparse but has found that unhoused individuals are more likely to enter residential SUD treatment and less likely to enroll in outpatient treatment when compared to housed individuals.(5) As unstable housing status, SUD, and traumatic injury are closely and reflexively related, the emergency department or hospital encounter for a traumatic injury is a unique opportunity to assess and address the needs of PEH with SUD. To our knowledge, there is no data exploring the influence of housing status on SUD treatment enrollment following a traumatic injury. The aim of this study was to examine the impact of housing status on SUD treatment engagement after traumatic injury in patients with SUD.

Methods: We conducted a retrospective cohort study of adult (age ≥18) trauma patients with SUD and known housing and treatment enrollment status at an urban, safety-net Level 1 trauma center from January 2021 to December 2022 (N = 618). Data was collected through detailed chart review. SUD treatment enrollment was defined as engagement with either behavioral or medication-based SUD treatment documented in the medical record. Univariate analyses were performed using Chi-square, Wilcoxon rank sum, and two-tailed t-tests. Multivariable logistic regressions controlling for demographic, clinical, and socioeconomic factors were used to evaluate the relationship between housing status and the primary outcomes: SUD treatment initiation and all SUD treatment enrollment within one year of the index encounter Treatment initiation was defined as new enrollment in SUD treatment within one year after the index encounter. All treatment enrollment was more broadly defined as any SUD treatment engagement within one year after the index encounter, including those enrolled in treatment prior to the index encounter that continued treatment during the study period. A p-value ≤ .05 was considered significant.

Results: Unhoused patients made up 38.7% (239) of the total study cohort (N = 618). Unhoused patients (mean (M)=44.3, SD 10.3) were more often younger than housed patients (M=50.87, SD 14.7), t(608) = 6.69, P<.001. Unhoused patients were also more often white (X2 (2, N = 618) = 12.1, p=.002), unemployed (X2 (2, N = 618) = 43.3, p<.001), and previously diagnosed with a mental health disorder (X2 (1, N = 618) = 20.8, p<.001) when compared to housed patients. Unhoused patients more frequently had multiple SUD diagnoses (153/239, 64.0%), and a sole alcohol use disorder diagnosis was more common in housed patients (193/378, 51.1%) (X2 (3, N = 618) = 48.7, p<.001). After regression controlling for demographic and clinical factors (age, sex, race, and Injury Severity Score), unhoused status was an independent positive predictor of both treatment initiation (odds ratio (OR) 4.92 95% CI 3.06-8.03) and all treatment enrollment (OR 4.04 95% CI 2.79-5.88). In regression controlling for employment and past medical history (SUD type, co-existing mental health diagnosis, and employment), unhoused status was again an independent positive predictor of both treatment initiation (OR 4.92 95% CI 3.06-8.04) and all treatment enrollment (OR 3.51 95% CI 2.38-5.21). All treatment enrollment was significantly lower for Alcohol Use Disorder only patients compared to Opioid Use Disorder only patients (OR 0.25 95% CI 0.13-0.49). A co-occuring mental health diagnosis was a positive independent predictor of both treatment initiation (OR 2.84 95% CI 1.75-4.66) and all treatment enrollment (OR 2.79 95% CI 1.91-4.13).

Conclusion & Discussion: Unhoused status was positively associated with both SUD treatment initiation and all treatment enrollment within one year of traumatic injury. This may be due to treatment enrollment requirements in facilities unhoused patients are discharged to and the fact that inpatient SUD treatment often addresses unmet basic needs (shelter, food). These results support that hospital encounters for traumatic injuries are a pivotal opportunity for treatment enrollment for unhoused patients.
Additionally, this study revealed that housed patients were less likely to initiate or maintain enrollment in SUD treatment after a traumatic injury. Compared to unhoused patients, determining the discharge disposition of housed patients less often requires addressing a co-occuring SUD, so the SUD may be less likely to be assessed during the hospital admission.
A limitation of this study is that we exclusively measured treatment enrollment. Future studies should also assess the role of housing status in the frequency and duration of engagement in SUD treatment.
Given the association between substance use and traumatic injury and the disparities in treatment enrollment highlighted in this study, we conclude that targeting addiction health services to all trauma patients is a potent use of resources likely to increase enrollment in SUD treatment.

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3. Miller JP, O’ Reilly GM, Mackelprang JL, Mitra B. Trauma in adults experiencing homelessness. Injury. 2020;51(4):897-905. doi:10.1016/j.injury.2020.02.086
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5. Han BH, Doran KM, Krawczyk N. National trends in substance use treatment admissions for opioid use disorder among adults experiencing homelessness. Journal of Substance Abuse Treatment. 2022;132:108504. doi:10.1016/j.jsat.2021.108504