Harms associated with injecting in public spaces: a global systematic review and meta-analysis

Background: Despite increasing backlash against harm reduction efforts and the need to understand the risk environments encountered by people who inject drugs (PWID), a quantitative systematic review on public injecting and associated health and drug-related outcomes is lacking. We aimed to summarize the global evidence on the prevalence and harms associated with injecting in public spaces. Methods: We searched MEDLINE, Embase, PsycINFO, CINAHL, Scopus, Global Health, and Web of Science from inception to March 21, 2024. We pooled data from included studies using random-effects meta-analyses to quantify the associations between recent (i.e., current or within the last year) public injecting and associated outcomes. Public injecting was defined as injecting in public or semi-public spaces, including streets, parks, and abandoned buildings. Risk of bias was assessed using the Joanna Briggs Institute's critical appraisal tool. Results: Of the 6144 initial records, 84 studies were eligible for inclusion. The pooled prevalence of recent public injecting was 48.85 % (95 % confidence intervals [CI] 43.87, 53.85). Public injecting was associated with increased odds of recent non-fatal overdose (odds ratio [OR] 2.51, 95 % CI 2.01, 3.13), HCV infection (OR 1.55, 95 % CI 1.18, 2.02), recent needle/syringe sharing (OR 2.41, 95 % CI 1.97, 2.94), recent sex work (OR 1.75, 95 % CI 1.03, 2.97), recent incarceration (OR 2.10, 95 % CI 1.78, 2.47), and recent unstable housing/homelessness (OR 4.23, 95 % CI 3.17, 5.65). Public injecting showed a statistically non-significant association with HIV infection (OR 1.41, 95 % CI 0.80, 2.46). Public injecting was also associated with a higher willingness to use supervised injection facilities (OR 2.66, 95 % CI 1.86, 3.80). Conclusion: Public injecting is prevalent among PWID and associated with various adverse drug- and health-related outcomes, highlighting the need for increased access to safe injection spaces. Findings support developing interventions to reduce harms from public injecting, such as addressing structural risks from law enforcement, expanding naloxone programs, and establishing overdose prevention centers. Housing interventions, in particular, could serve as an effective upstream strategy to reduce public injecting and related harms.