Substance use treatment utilization and unmet demand among recently incarcerated syringe services program participants in Washington state

People who use drugs are disproportionately impacted by incarceration and face elevated overdose risk following release. Despite this heightened risk, access to evidence-based substance use disorder (SUD) treatment—particularly medications for opioid use disorder (MOUD)—remains limited. This study examined the association between past-year incarceration and SUD treatment utilization and unmet treatment demand among Washington State syringe services program (SSP) participants. Participants were surveyed across SSPs in 25 counties between October 2023 and January 2024 (N=1,661). Bivariate comparisons between respondents with and without past-year incarceration were conducted using Pearson χ 2 tests. Three multivariable logistic regression models examined associations between past-year incarceration and: (1) receipt of any past-year SUD treatment, (2) receipt of MOUD, and (3) unmet SUD treatment demand (defined as inability to access requested help). Models adjusted for demographics, overdose history, housing, insurance, and past-week substance use, using cluster-robust standard errors at the SSP site level. Adjusted odds ratios and average marginal effects (AMEs) were calculated. Thirty percent (n=502) of respondents reported past-year incarceration. Compared with those without incarceration, recently incarcerated participants were younger, more likely to identify as men, and more likely to report homelessness (all p < 0.001). They also reported higher prevalence of past 3-month overdose (32% vs. 20%; p < 0.001) and concurrent opioid and stimulant use (68% vs. 55%; p < 0.001). In adjusted analyses, past-year incarceration was associated with a higher predicted probability of receiving any SUD treatment (44.8% vs. 30.3%; AME=0.14; 95% CI 0.09–0.19; p < 0.001) and reporting unmet treatment demand (37.1% vs. 29.7%; AME=0.07; 95% CI 0.02–0.12; p = 0.01). Incarceration was not significantly associated with MOUD receipt ( p = 0.09). Insurance coverage was strongly associated with MOUD utilization; uninsured respondents had a substantially lower predicted probability of receiving MOUD (6.3% vs. 31.1%; AME=−0.25; 95% CI −0.31 to −0.19; p < 0.001). Recently incarcerated SSP participants experience a paradox of greater SUD treatment receipt alongside higher unmet demand and no increase in MOUD utilization. Strengthening low-barrier MOUD access within SSPs may improve treatment continuity and reduce overdose risk during reentry.