BACKGROUND: With a rising prison population, a substantial portion of whom are identified as substance misusers, it is important to understand the availability of treatment pathways, their successes and areas for improvement. Given the likely importance of national factors in criminal justice and substance use service provision, we chose to focus on one country.

AIM: To review substance misuse treatment and outcomes for such treatments as implemented in British prisons for men.

METHODS: We conducted a mixed-methods systematic review, searching Ovid MEDLINE, Ovid Embase, APA PsycINFO, CINAHL Plus, Sociology Collection, Web of Science Core Collection and Social Science Premium Collection between 1 January 2000 and 5 June 2024. Included were empirical, peer-reviewed studies of processes and outcomes of UK male prison-based substance misuse programmes. Primary outcomes included changes in substance use, withdrawal symptoms and experiences of interventions, whereas secondary outcomes encompassed quality of life, locus of control and mental health. Because of study design heterogeneity, meta-analysis was not possible. Analysis followed JBI methodology with a convergent synthesis.

RESULTS: Fourteen studies were included: 8 qualitative, 5 quantitative studies of which 3 were randomised control trials (RCTs) and 1 mixed-methods study, with a combined sample of 4037 participants engaged in opioid substitute treatment (OST) and/or psychosocial interventions. Four key themes emerged: the power of purposeful activity, strengthening support systems, bridging patient needs with treatment plans and, for those in opiate programmes, experiences and engagement with opioid substitution treatments.

CONCLUSIONS: Participants articulated diverse treatment needs, highlighting the necessity of individualised and tailored reduction or maintenance plans. Treatment requires a comprehensive approach with the aim of facilitating effective social integration.