People who inject drugs face a wide range of health, social and structural inequities, including risk of overdose, HIV and hepatitis C infections, homelessness and housing instability, incarceration, and mental health challenges. Injection in public spaces has been linked to increased risk of overdose, infectious disease and other serious harms, particularly among people who are homeless or unstably housed and lack access to safe, private places to inject. This article summarizes a systematic review and meta-analysis that examined harms associated with injecting in public spaces.
What kind of research did the systematic review include?
The systematic review included 84 articles published between 2000 and 2024. Fifty-two of these studies were subsequently included in the meta-analysis. Public injecting was defined as injecting in a public or semi-public space (e.g., streets, parks, subway stations, ATM enclosures, malls, public restrooms, building hallways, abandoned buildings). An article was included if it:
- was an original quantitative study that reported on public injecting or its relationship with health- and drug-related harms
- had an entire sample of people who inject drugs or if the data from people who inject drugs could be separated from the entire sample (i.e., disaggregated)
- had a sample size of 60 people or greater
The studies in the review had the following characteristics: sample sizes ranged from 62 to 16,132 participants and median ages ranged from 21 to 47 years. Articles included in the review reported data from cross-sectional and longitudinal studies.
Most studies presented data from Canada (35 studies), the United States (18 studies), Australia (10 studies), the United Kingdom (6 studies), Mexico (4 studies) and Iran (2 studies). One study each was included from Thailand, The Netherlands, Ukraine, Spain, Kosovo, Colombia, Kyrgyzstan, Indonesia and Myanmar.
What are the harms associated with injecting in public spaces?
Prevalence of public injection
Forty-one studies examined the prevalence of injecting in public spaces within the past year (i.e., how common it is). Combined, these studies found that 48.9% of people who injected drugs reported public injection during that period.
Non-fatal overdose
Across 14 studies, people who injected in public had more than double the odds of non-fatal overdose compared with those who did not inject in a public space (odds ratio [OR] = 2.51).
HIV and hepatitis C infections
Across six studies, people who reported public injecting had significantly higher odds (OR = 1.55) of hepatitis C infection. Among four studies, people who injected in public tended to have a higher odds of HIV infection, although the estimate was not statistically significant (OR = 1.41).
Five studies examined HIV-related outcomes. One study found that public injecting was associated with worse health outcomes among people living with HIV, including double the odds of having a detectable viral load (OR = 2.05), lower odds of engaging in antiretroviral therapy (OR = 0.39) and lower odds of having a higher CD4 count (per 100 cells/mL) (OR = 0.93).
Drug use and sex work
Across 17 studies, public injecting was significantly associated with sharing needles or syringes (OR = 2.41). Studies also found that people who injected in public had more than five times the odds of rushing their injections (OR = 5.57). Public injecting was also associated with higher frequency of injection (OR range = 1.96–5.34), binge drug use (OR range = 1.27–2.88), binge or heavy alcohol use (OR range = 1.33–3.35) and initiating others into injecting drugs (OR = 1.38). Combined results from five studies showed that public injecting was associated with recent involvement in sex work (OR = 1.75).
Incarceration, unstable housing and homelessness
Nine studies showed public injecting was associated with double the odds of arrest or incarceration (OR = 2.1). Fifteen studies found that people who injected in public had over four times the odds of recent unstable housing or homelessness (OR = 4.23).
Skin and soft tissue infections
Four studies reported that public injection was associated with skin and soft tissue infections (OR = 1.67), lumps and swelling in injection sites (OR = 2.26), prominent scarring and bruising in injection sites (OR = 2.86), injection-related injury and disease (OR = 1.90) and other injection-related complications (OR = 1.33).
Mental health outcomes
Three studies showed that public injection was associated with higher odds of mental health issues. Injecting in public spaces was significantly associated with psychological distress (OR = 2.57), suicidal ideation (OR = 1.91) and self-harm (OR = 1.87).
Willingness to use supervised consumptions sites (SCS), and use of these sites
Eight studies reported that public injection was associated with significantly higher odds of being willing to use SCS (OR = 2.66). Public injecting was also associated with higher odds of accessing an SCS (OR range = 1.65–2.61) and of accessing on-site withdrawal management services (i.e., detox) at an SCS (OR = 4.14).
Informal drug consumption settings and associated outcomes
Six studies looked at the association between the use of informal drug consumption settings (i.e., locations where people who inject drugs gather and may share injection equipment) and drug- and health-related outcomes. Four studies found the use of informal drug consumption settings was associated with significantly higher odds of HIV infection (OR range = 2.0–5.99). Five studies reported increased odds of hepatitis C infection (OR range = 1.83–2.90). People who injected drugs in an informal setting were 2.4 times more likely to test positive for hepatitis B. Three studies reported that people who injected drugs in informal settings were more likely to reuse a needle after someone else had used it (OR range = 2.36–3.60).
What are the implications of the review for service providers?
This review shows that public injecting is common, with roughly half of the people who inject drugs included in this systematic review and meta-analysis reporting injecting in public spaces. Public injecting is linked to a wide range of harms, including higher risk of non-fatal overdose; HIV and hepatitis C transmission; mental health challenges; skin and soft tissue infections; and arrest or incarceration. It also often occurs alongside behaviours that can increase the risk of harms such as rushed injections and sharing equipment. Importantly, people who inject in public show a greater willingness to use SCS, highlighting an opportunity to reach those at risk.
For frontline service providers, these findings highlight the importance of meeting people where they are, particularly in public or informal injecting settings. Expanding access to sterile drug use equipment, naloxone, overdose prevention education and HIV and hepatitis C prevention resources in areas where public injecting occurs can directly reduce harms. Providers can also support mental health needs and connect people to housing resources, recognizing that homelessness and housing instability are strongly linked to public injecting. Reaching people in public injecting spaces also provides opportunities to guide people toward SCS (where they exist), which can offer a safer environment for injection, prevent overdoses and connect people to other health and social services. Broader policy changes such as expanding SCS and Housing First initiatives can enable frontline staff to play a crucial role in linking people to these services and reducing immediate harms in public spaces.
When considering this review, it is important to remember the following:
Data quality and quantity varied by country, making it hard to provide accurate global estimates. Most studies came from high-income countries, with few from low- and middle-income regions. Inconsistent reporting and study variations limited detailed analysis. Some studies focused on street-involved participants, possibly overestimating public injecting rates. The inclusion of cross-sectional studies made it hard to track changes over time. Small studies (under 60 participants) were excluded, potentially omitting valuable data. While most studies were rated as fair quality, bias (e.g., selection and recall bias) is still a concern, and the differences between studies make the findings less precise. Results should be interpreted cautiously.
What is a systematic review?
Systematic reviews are important tools for informing evidence-based programming. A systematic review is a critical summary of the available evidence on a specific topic. It uses a rigorous process to identify all the studies related to a specific research question. Relevant studies can then be assessed for quality and their results summarized to identify and present key findings and limitations. If studies within a systematic review contain numerical data, these data can be combined in strategic ways to calculate summary (“pooled”) estimates. Combining data to produce pooled estimates can provide a better overall picture of the topic being studied. The process of pooling estimates from different studies is referred to as a meta-analysis.
Reference
Khezri M, Kimball S, McKnight C et al. Harms associated with injecting in public spaces: a global systematic review and meta-analysis. International Journal of Drug Policy. 2025 Jun 1;140: 104819. Available from: https://www.sciencedirect.com/science/article/abs/pii/S0955395925001185
About the author(s)
Alex Holtom was CATIE’s knowledge specialist in harm reduction programming. She has a master of social work degree in international and community development and previously worked in frontline harm reduction service provision.