Substance use-related stigma and injection-related bacterial infections among people who inject drugs in Montreal

Evidence quantifying dimensions of stigma and their health impacts among people who inject drugs (PWID) remains limited. We characterized substance use-related stigma dimensions among PWID and estimated their associations with injection-related bacterial infections (IRBIs).

We conducted a cross-sectional study nested within a prospective cohort of PWID in Montréal (August 2024-November 2025). Substance use-related stigma was measured using the Substance Use Stigma Mechanisms Scale (SU-SMS), capturing three mechanisms (enacted/anticipated/internalized); enacted and anticipated stigma were further stratified by source (family/healthcare workers). Mean scores were computed for each dimension (range 1-5) and dichotomized as low (<4) or high (≥4); any stigma was defined as high if ≥1 mechanism was high. IRBIs in the past three months included skin/soft tissue infections, bone/joint infections, sepsis, or endocarditis. Associations with IRBIs were estimated for each stigma mechanism, and by source, using Poisson regression with robust standard errors.

Among 377 PWID, high enacted, anticipated, and internalized stigma were reported by 10%, 10%, and 9%, respectively. High stigma on any mechanism was reported by 20%. By source, high family-related stigma was more prevalent than healthcare-related stigma for both enacted (30% vs 11%) and anticipated stigma (26% vs 12%). Recent IRBIs were reported by 23% of participants. Associations with recent IRBIs were strongest for enacted stigma, with those reporting high (vs low) levels twice as likely to report one (adjusted prevalence ratio [aPR]=2.1; 95%CI: 1.4-3.1); however, associations were modest and inconclusive for anticipated (aPR=1.3; 95%CI: 0.8-2.1) and internalized stigma (aPR=1.2; 95%CI: 0.7-2.2). When stratified by source, enacted stigma remained associated with IRBIs whether from family or healthcare workers, whereas anticipated stigma showed no clear association from either source.

One in five PWID experienced high substance use-related stigma on at least one of the three mechanisms. Findings underscore the multifaceted, harmful impact of stigma on PWID health and the need to address stigma from both family members and healthcare workers.