BACKGROUND AND AIMS: People who use drugs are overrepresented in the criminal justice system. We aimed to provide a broad synthesis of the epidemiology, harms and interventions related to drug use and drug use disorders among incarcerated adults worldwide, and highlight gaps in evidence and practice.

METHODS: In this structured review, we searched PubMed and Web of Science for articles published between 2015 and August 2025. Systematic reviews, meta-analyses and large primary studies with unselected samples were given preference for inclusion.

RESULTS: Four in ten adults who enter prison meet diagnostic criteria for a drug use disorder, a treatable psychiatric condition often underlying the offences that led to their incarceration. Drug use disorders are approximately ten times more prevalent among people in prison compared with the general population, with a higher excess in women. Comorbid mental disorders are common. Around a third of incarcerated individuals report using drugs during imprisonment, which poses a health and safety risk for people both living and working in prisons. Injecting drug use in prison contributes to blood-borne virus transmission. In addition to its strong link with recidivism, drug use is associated with a markedly increased risk of premature mortality after release from prison, particularly from drug-related causes within the first two weeks post-release. Despite robust evidence supporting the effectiveness of prison-based pharmacological (e.g. opioid agonist treatment) and psychosocial (e.g. therapeutic communities) interventions in reducing drug-related harms, there remains a significant treatment gap within prison settings worldwide. Further research is needed to assess the health benefits of harm reduction services in prisons, including needle and syringe programmes. Strategies to facilitate linkage to and retention in post-release services are key to ensure continuity of care and achieve sustainable treatment outcomes.

CONCLUSION: The high prevalence of drug use and its multiple adverse outcomes among people in prison underscore the need for provision of evidence-based interventions. Expanding and integrating prison-based and post-release interventions to address drug use has the potential to yield both public health and criminal justice benefits.