Michael John Milloy

Background: Housing is a key determinant of health. In response to increasingly visible homelessness amid a growing housing crisis, many jurisdictions in North America forcibly displace unhoused people from public spaces, routinely confiscating their personal belongings. While prior research demonstrated various health-related harms associated with these “encampment sweeps,” the impact on housing placements among otherwise unhoused people remains unclear. We sought to estimate the relationship between experiencing encampment sweeps and transitioning from homelessness among unhoused people who use drugs in Vancouver, Canada. Methods and findings: Data were derived from two harmonized prospective cohort studies of people who use drugs in Vancouver, followed through semi-annual interviews between December 1, 2021 and May 31, 2025. We used proportional hazard marginal structural modeling (MSM) to examine if experiencing municipal government-enforced confiscation of personal belongings was associated with no longer reporting homelessness in the past 6 months during follow-up among unhoused participants after adjusting for a range of potential time-varying confounders including demographic characteristics, drug use patterns, health status and other social/structural exposures. A secondary analysis replaced confiscation of belongings with municipal government-enforced forced displacement that may have not involved confiscation of belongings between June 1, 2023 and May 31, 2025. Among 235 participants, 59 (25.1%) reported confiscation of their belongings at baseline. During follow-up, 128 (54.5%) stopped reporting homelessness, corresponding to an incidence rate of 55.6 (95% confidence interval [CI]: 46.4, 66.1) cases per 100 person-years. In the secondary analysis, 50 (32.5%) of 154 participants reported forced displacement at baseline and 62 (40.3%) stopped reporting homelessness during follow-up. In the proportional hazard MSM, confiscation of belongings (adjusted hazard ratio [AHR]: 0.35; 95% CI [0.13, 0.94]; p = 0.036) and forced displacement (AHR: 0.07; 95% CI [0.02, 0.20]; p < 0.001) were both negatively associated with transitioning from homelessness. Main limitations include potential overestimation of rates of transitioning from homelessness and limited causal inference due to the observational study design. Conclusions: The confiscation of personal belongings and forced displacement might undermine pathways to housing. Our findings underscore the need for policy approaches that prioritize access to dignified and affordable housing rather than practices that perpetuate homelessness. Future research should assess the quality of housing that unhoused people are placed in and examine how it relates to returning to homelessness.

Background: Opioid withdrawal is a significant challenge for people seeking to reduce or eliminate opioid use, and unmanaged withdrawal increases the risk of relapse and overdose. Using cannabis to manage opioid withdrawal has been reported by people who use opioids, yet it is not clear whether this leads to reductions in opioid use. Moreover, because pain is prevalent among people who use unregulated opioids (PWUO) and may contribute to ongoing opioid use, the effects of cannabis use to manage withdrawal symptoms may differ among individuals experiencing moderate to severe pain. We investigated the relationship between cannabis use to manage unregulated opioid withdrawal and self-reported reductions in opioid use among PWUO. Methods: Data were derived from a cross-sectional questionnaire administered to cannabis-using PWUO in Vancouver, Canada, between December 2019 and November 2021. Multivariable logistic regression estimated the associations between cannabis use for opioid withdrawal and self-reported reductions in opioid use. A sub-analysis explored if these associations varied among participants living with and without moderate to severe pain. Results: Among 197 participants, 89 (45.2%) reported cannabis use to manage symptoms of opioid withdrawal in the past six months. In multivariable analysis, cannabis use for opioid withdrawal was significantly associated with self-reported reductions in opioid use (adjusted Odds Ratio [AOR] = 2.16, 95% Confidence Interval [CI]: 1.13–4.19) in the same time period. In a sub-analysis, this association was only significant among participants with moderate to severe pain (AOR = 6.55; 95% CI: 2.44–19.63). Conclusions: We observed a significant association between self-reported use of cannabis to manage unregulated opioid withdrawal and reductions in opioid use among cannabis-using PWUO living with pain. Aligned with other studies, these findings support conducting experimental trials of cannabinoids to support individuals experiencing opioid withdrawal and living with pain.

Introduction: Gabapentin is widely prescribed off‐label to treat pain. However, there are concerns about the proliferation of medical and non‐medical use, and the potential increased risk of overdose death associated with concurrent opioid use. Despite these considerations, prescription gabapentin use among people who use unregulated drugs is uncharacterised in Canada. Therefore, we investigated trends and factors associated with being prescribed gabapentin for pain among community‐recruited people who use opioids. Methods: Data were derived from three prospective cohort studies of people who use unregulated drugs in Vancouver, Canada, restricted to periods of opioid use (i.e., unregulated use, non‐medical use, and/or opioid agonist treatment). We characterised factors associated with reporting gabapentin for pain between 2014 and 2020 using multivariable generalised estimating equations. Trends in self‐reported prescription (2014–2020) and non‐medical (2016–2024) gabapentin use were explored. Results: Between 2014 and 2020, we included 10,999 observations from 2039 participants who had a baseline median age of 38 years and were 62.4% male and 57.5% White. Gabapentin prescriptions for pain were reported by 255 (12.5%) participants. Observations reporting a neuropathic pain diagnosis had 3.54 times the adjusted odds (95% CI 2.81, 4.46) of being prescribed gabapentin. From 2014 to 2020, the prevalence of gabapentin prescriptions rose from 5.4% to 7.8%. Non‐medical gabapentin use remained low. Discussion and Conclusions: Among people who use opioids, we observed an increase in gabapentin prescriptions for pain between 2014 and 2020. Gabapentin prescriptions were strongly associated with reporting a neuropathic pain diagnosis. Rates of non‐medical gabapentin use were substantially lower than rates reported internationally.

Introduction: Amidst the opioid overdose crisis, there is interest in cannabis use for pain management and harm reduction. We investigated the relationship between cannabis use and cessation of unregulated opioid use among people who use drugs (PWUD) living with chronic pain.Method: Data for analyses were collected from three prospective cohort studies in Vancouver, Canada. All cohort participants who completed at least two study visits and reported both pain and unregulated opioid use in the past 6 months were included in the present study. We analysed the association between cannabis use frequency and opioid cessation rates using extended Cox regression models with time‐updated covariates.Results: Between June 2014 and May 2022, 2340 PWUD were initially recruited and of those 1242 PWUD reported chronic pain, use of unregulated opioids and completed at least two follow‐up visits. Of these 1242 participants, 764 experienced a cessation event over 1038.2 person‐years resulting in a cessation rate of 28.5 per 100 person‐years (95% confidence interval [CI] 25.4–31.9). Daily cannabis use was positively associated with opioid cessation (adjusted hazard ratio 1.40, 95% CI 1.08–1.81; p = 0.011). In the sex‐stratified sub‐analyses, daily cannabis use was significantly associated with increased rates of opioid cessation among males (adjusted hazard ratio 1.50, 95% CI 1.09–2.08; p = 0.014).Discussion and Conclusions: Participants reporting daily cannabis use exhibited higher rates of cessation compared to less frequent users or non‐users. Observed sex‐specific differences in cannabis use and opioid cessation suggest potential differences in cannabis use behaviours and effects. Our findings add to the growing evidence supporting the potential benefits of cannabis use among PWUD, underlining the need for further research.

Introduction The Road to Recovery (R2R) Initiative is an innovative model of substance use care that seeks to increase treatment capacity by creating approximately 100 new addiction treatment beds to provide on-demand addiction care in Vancouver, British Columbia, for patients with substance use disorders. The new model also coordinates the region’s existing clinical substance use services to support patients across a care continuum that includes traditional office-based addiction treatment and harm reduction services, early withdrawal management and more intensive abstinence-based treatment programming. To understand the impact of offering on-demand and coordinated substance use care, an observational cohort of individuals who access any R2R clinical service will be created to examine health and social outcomes over time. Methods and analysis This prospective mixed-methods study will invite individuals from Vancouver, Canada, who access substance use treatment through the R2R model of care to (1) complete a baseline and 12-month follow-up quantitative questionnaire that solicits sociodemographic, substance use and previous addiction treatment data and (2) provide consent to the use of participants’ personal identifiers to access health records for chart review and for annual linkage to select health and administrative databases to allow for ongoing (virtual) community follow-up over 5 years. Additionally, a purposive sample of cohort participants will be invited to participate in baseline and 12-month follow-up qualitative interviews to share their experiences accessing R2R and identify challenges and opportunities associated with the implementation of R2R. Ethics and dissemination The study was approved by the University of British Columbia Providence Health Care Research Ethics Board in September 2023. Results from the proposed study will be published in peer-reviewed journals, presented at national and international scientific conferences and disseminated through regular meetings with policymakers, individuals with lived and living experience, and other high-level stakeholders, academic presentations and lay media.

We sought to evaluate the rates and predictors of SARS-CoV-2 vaccination among members of a structurally-marginalized population of people who use drugs (PWUD) during a targeted, community-wide, vaccination campaign in Vancouver, Canada. Interviewer-administered data were collected from study participants between June 2021 and March 2022. Generalized estimating equation analysis was used to identify factors associated with SARS-CoV-2 vaccine uptake, ascertained through a province-wide vaccine registry. Among 223 PWUD, 107 (48.0%) reported receipt of at least two SARS-CoV-2 vaccine doses at baseline and this increased to 151 (67.7%) by the end of the study period. Using social media as a source of vaccine information was negatively associated with SARS-CoV-2 vaccine uptake (Adjusted odds ratio [AOR] 0.27, 95% confidence interval [CI] 0.09–0.81) and HIV seropositivity (AOR 2.68, 95% CI 1.12–6.39) and older age (AOR 1.27, 95% CI 1.07–1.51) were positively associated with SARS-CoV-2 vaccine uptake. These findings suggest that the targeted vaccination campaign in Vancouver may be an effective model to promote SARS-CoV-2 vaccination in other jurisdictions. However, using social media as a source of vaccine information likely reduced SARS-CoV-2 vaccine uptake in PWUD arguing for further efforts to promote accessible and evidence-based vaccine information among marginalized populations.

Introduction: While substance use contributes to a substantial burden of disease, access to evidence-based harm reduction interventions remains limited or inaccessible. Preliminary research suggests that some individuals use cannabis to reduce the harms associated with their use of other substances, including opioids and stimulants. This study examines factors associated with the self-reported use of cannabis for harm reduction among people who use drugs (PWUD). Methods: We drew data from three prospective, community-recruited cohorts of PWUD in Vancouver, Canada, between June 2016 and May 2018. Multivariable generalized linear mixed-effects modeling was used to examine factors associated with the primary outcome of “use of cannabis for harm reduction,” defined as self-reported use of cannabis to substitute for other substances, treat withdrawal, or come down off other drugs. Results: One thousand nine hundred thirty-six participants contributed 5706 observations. In adjusted analyses, daily methamphetamine use (adjusted odds ratio [AOR]=1.43, 95% confidence interval [CI]: 1.09–1.89), experiencing barriers to accessing addiction treatment (AOR=1.92, 95% CI: 1.21–3.03), and enrollment in addiction treatment modalities other than opioid agonist therapy (AOR=1.64, 95% CI: 1.17–2.29) were positively associated with using cannabis for harm reduction. Older age was negatively associated (AOR=0.97, 95% CI: 0.95–0.98). Among 1281 (66.2%) participants who use cannabis, daily cannabis use and obtaining cannabis from unregulated dispensaries were also independent correlates of using cannabis for harm reduction. Discussion and Conclusions: Individuals who were more likely to use cannabis for harm reduction reported difficulty accessing addiction treatment or used substances, such as methamphetamines, where effective treatments are limited. These findings highlight the need to better understand the potential harm-reducing impacts of cannabis among PWUD in these scenarios.

Although prevalent among people living with human immunodeficiency virus (HIV) (PLWH) and people who use unregulated drugs (PWUD), pain and its possible links to substance use patterns and engagement in HIV treatment remains poorly characterized. We sought to evaluate the prevalence and correlates of pain among a cohort of PLWH who use unregulated drugs. Between December 2011 and November 2018, 709 participants were recruited, and data were analyzed using generalized linear mixed-effects (GLMM). At baseline, 374 (53 percent) individuals reported moderate-to-extreme pain in the previous 6 months. In a multivariable model, pain was significantly associated with nonmedical prescription-opioid use (adjusted odds ratio (AOR) = 1.63, 95 percent confidence interval (CI): 1.30-2.05), nonfatal overdose (AOR = 1.46, 95 percent CI: 1.11-1.93), self-managing pain (AOR = 2.25, 95 percent CI: 1.94-2.61), requesting pain medication in the previous 6 months (AOR = 2.01, 95 percent CI: 1.69-2.38), and ever being diagnosed with a mental illness (AOR = 1.47, 95 percent CI: 1.11-1.94). Establishing accessible pain management interventions that address the complex intersection of pain, drug use, and HIV-infection has potential to improve quality of life outcomes among this population.

Background: Methadone maintenance treatment (MMT) is an effective treatment for opioid use disorder. However, subtherapeutic dosing may lead to continued opioid use by failing to suppress opioid withdrawal and craving. Preclinical and pilot experimental research suggests that cannabinoids may reduce opioid withdrawal and craving. We sought to test whether the association between low methadone dose and illicit opioid use differs according to concurrent cannabis use patterns. Methods: Data for this study were derived from two community-recruited cohorts of people (≥18 years old) who use illicit drugs in Vancouver, Canada. We used generalized estimating equations to estimate the adjusted association between lower daily MMT dose (p <0.01) between daily cannabis and lower MMT dose on concurrent daily illicit opioid use: lower MMT doses increased the odds of daily illicit opioid use by 86% (adjusted odds ratio [AOR]=1.86, 95% confidence interval [CI]=1.61–2.16) during periods of no or low-frequency cannabis use and by 30% during periods of daily cannabis use (AOR=1.30, 95% CI=1.01–1.67). Discussion: This study provides preliminary observational evidence that cannabis may mitigate some of the negative effects of subtherapeutic MMT dosing, guiding future clinical investigations into the safety and efficacy of cannabis and cannabinoids as adjunct treatment for MMT.

People living with HIV (PLWH) often experience stigma and discrimination by health care professionals. We investigated the prevalence of perceived mistreatment in health care settings and its associations with HIV clinical outcomes and health care-seeking behaviour using data from a long-running prospective cohort of PLWH who use drugs. Of the 857 participants included, 19% reported at least one instance of perceived mistreatment during the study period. In adjusted longitudinal analyses, perceived mistreatment was positively associated with not being on ART in the same follow-up period, and participants who reported perceived mistreatment were less likely to report seeing a physician in the subsequent follow-up period. Daily use of injection drugs was positively associated with reporting perceived mistreatment. These findings demonstrate the implications of negative health care interactions in a population that must consistently engage with the health care system, and the need for stigma-reducing educational interventions for health care professionals.