INTRODUCTION: People experiencing homelessness and alcohol dependence are vulnerable to a range of harms, and existing treatment options, which are often abstinence-based, are inadequate for this group because they may be unavailable, unsuitable, or not aligned with goals. Abstinence-based treatment programmes also rarely address underlying social and health issues faced by this population. Instead, alcohol harm reduction approaches provide individuals with support to reduce the harms associated with their drinking, without the need to stop drinking. Managed alcohol programmes (MAPs) are one harm reduction approach specifically designed for this group. MAPs provide alcohol in regulated doses through the day, alongside wider support for housing, physical and mental health, welfare, and social connections.

METHODS: A realist review was conducted to explore the current evidence base for MAPs. Realist reviews aim to synthesise existing evidence to examine the contexts, mechanisms, and outcomes of complex interventions, on the assumption that the outcomes of these interventions are directly caused by underlying mechanisms which have been activated in particular contexts. Twenty-four initial programme theories were developed and then tested using international evidence and refined to 11 programme theories.

RESULTS: A total of 60 sources were included in this review, highlighting a range of contexts, mechanisms, and outcomes relating to MAPs. The 11 programme theories demonstrate the need for MAPs in a context where abstinence-based treatment is the norm but is often unsuitable for this population. For MAPs to be successful for this population they need to enable autonomy, address clients' needs, create a sense of hope and purpose, and provide access to healthcare and other activities. MAPs can lead to a range of positive outcomes for those who access them.

CONCLUSIONS: Our theoretically informed exploration of service implementation can inform the design, development, and optimisation of future MAPs internationally. At a time when homelessness and alcohol deaths are increasing, innovative harm reduction approaches like MAPs are required to improve wellbeing and support health contextualised by the complex lives faced by some individuals.