Engager logo

Background and aims

The great majority of male prison-leavers in the UK have significant mental health problems, including anxiety, depression, substance misuse and traits associated with the diagnostic label of personality disorder. Only a minority receive mental health care on release from prison. The aim of the Engager Research Programme was to develop and evaluate a theory- and evidence-informed complex intervention designed to support individuals with mental health problems, before and after release from prison. 

Implications for policy and practice

The Engager programme ran from 2013-2020 and has generated an evidence based model for mental health care for prison leavers.
There are two areas where there are lessons for others:
  • Those developing and delivering the new Enhanced Reconnect services for high risk prison leavers – the Engager model has many similarities in that is designed to provide personalised wrap around care. The depth Engager process evaluation provides insights for practice and support to those delivering care.
  • Those voluntary, community or social enterprise (VCSE) services looking after individuals with complex needs in the community in the housing, substance misuse and criminal justice sectors – we propose a new model adapted from engager where an experienced specialist mental health worker provides supervision to the many support workers already providing mental health support outside of specialist services.

Please contact primarycare@plymouth.ac.uk to request a copy of the manual or gain advice from the research team on developing services based on the Engager model.


In phase one, the intervention was developed through a set of sub-studies: 
  1. A realist review of psycho-social care for individuals with complex needs;
  2. Case studies within services demonstrating promising intervention features; 
  3. Focus groups with individuals from underrepresented groups;
  4.  A rapid realist review of the intervention implementation literature;
  5. A formative process evaluation of the prototype intervention. 
In a parallel, randomised trial, methodological development included: 
  1. Selection of outcome measures through review of the literature, piloting of measures and a consensus process with stakeholders; 
  2. Development of ways to quantify treatment as usual and intervention receipt; 
  3. Piloting of trial procedures;
  4. Modelling economic outcomes. 
In phase two, we conducted: 
  1. An individually-randomised superiority trial of the Engager intervention; 
  2. A cost-effectiveness and cost-consequence analysis; 
  3. An in-depth mixed methods process evaluation.  
Patient and public involvement (PPI) influenced throughout the programme, primarily through the development and engagement of a Peer Researcher Group. 


  • Weston L, Rybczynska-Bunt S, Quinn C, Lennox C, Maguire M, Pearson M, et al. Interrogating intervention delivery and participants’ emotional states to improve engagement and implementation: a realist informed multiple case study evaluation of Engager. PLOS ONE 2022;17:e0270691. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0270691
  • Byng R, Kirkpatrick T, Lennox C, Warren FC, Anderson R, Brand SL, et al. Evaluation of a complex intervention for prisoners with common mental health problems, near to and after release: The Engager randomised controlled trial [published online ahead of print August 18 2022]. Br J Psych 2022. https://pubmed.ncbi.nlm.nih.gov/35978272/
  • Hunter RM, Anderson R, Kirkpatrick T, Lennox C, Warren F, Taylor R, et al. Economic evaluation of a complex intervention (Engager) for prisoners with common mental health problems, near to and after release: a cost-utility and cost-consequences analysis. Eur J Health Econ 2022;22:193–210. https://doi.org/10.1007/s10198-021-01360-7
  • Rybczynska-Bunt S, Weston L, Byng R, Stirzaker A, Lennox C, Pearson M, et al. Clarifying realist analytic and interdisciplinary consensus processes in a complex health intervention: a worked example of judgemental rationality in action. Evaluation 2021;27. https://doi.org/10.1177/13563890211037699
  • Lennox C, Stevenson R, Owens C, Byng R, Brand SL, Maguire M, et al. Using multiple case studies of health and justice services to inform the development of a new complex intervention for prison-leavers with common mental health problems (Engager). Health Justice 2021;9:6. https://doi.org/10.1186/s40352-021-00131-z

Further publications


Phase One

The Engager intervention development resulted in a clear worked example of using realist-informed approaches, which can be used as a blueprint for intervention development and trial preparation. A practitioner in prison offered participants practical and emotional support on the day of their release and for three to five months post-release. We also developed a theoretically-informed Intervention Delivery Platform (IDP) (training, manual, supervision) to support implementation.  
Our development of trial methodology was substantial; outcome measures were selected to represent a broad range of domains, with a general mental health outcome as the primary measure for the trial. Procedures for recruitment and follow-up included flexible approaches to engagement and retention. 

Phase Two 

Trial delivery was a significant logistical achievement. Two hundred and eighty individuals were randomised across three prison settings to receive Engager, plus usual care (n = 140) or usual care only (n = 140). We achieved an impressive follow-up rate of 65% at six months. 
We found no difference between the two groups for the Clinical Outcome in Routine Evaluation – Outcome Measure (CORE-OM) at six months. No differences in secondary measures and sensitivity analyses were found beyond those expected by chance. The cost-effectiveness analysis showed that Engager cost significantly more at £2,133 (95% of iterations between £997 to £3,374) with no difference in quality adjusted life years (QALY) -0.017 (95% of iterations between -0.042 to 0.007).  
The mixed methods process evaluation demonstrated implementation barriers.  These included problems with retention of the intervention team, and the adverse health and criminal justice system context. Seventy-seven percent (n = 108/140) of individuals had at least one community contact. Significant proportions of those engaging received day release work and practical support. In contrast, there was evidence that the psychological components, mentalisation and developing a shared understanding, were used less consistently. When engagement was positive, these components were associated with positive achievement of goals for individuals. We were also able to identify how to improve the intervention programme theory, for example, regarding how to support individuals who were overly unrealistic in their perception of their ability to cope with challenges post-release.

Strengths and limitations

Our development work was comprehensive, particularly given little prior evidence or theory specific to male offenders to build on. Our trial methodological development enabled the completion of the first fully-powered trial of a mental health intervention for prison leavers with common mental health problems. There were potential weaknesses in the trial methodology in terms of follow-up rates and outcome measures, with the latter potentially being insufficiently sensitive to be important, but highly individual changes in participants who responded to the intervention.


Delivering a randomised controlled trial for prison leavers with acceptable levels of follow-up is possible despite adverse conditions. Full intervention implementation was challenging. Some individuals did respond well to the intervention when both practical and psychological support were flexibly deployed as intended, with evidence that most components were experienced as helpful for some individuals. It is recommended that several key components be developed further, and tested, along with improved training and supervision to support delivery of the psychological aspects of the intervention in challenging conditions. 
Engager programme report (PDF) 

Patient and Public Involvement (PPI)

Active involvement of men who had previously served prison sentences was an integral part of the Engager intervention development and evaluation. The group who were self-coined as ‘Peer Researchers’ reflected that they brought their lived experience, the research team brought their academic experience, and that they all worked together as ‘peers’. They contributed to the design, delivery and evaluation of the Engager intervention inputting into: 
  • Trial science; including refining study documents such as invitation letters, consent forms, interview schedules and deciding on outcome measures, and explaining randomisation;
  • Qualitative data capture (co-facilitating focus groups allowing participants to feel more comfortable to contribute) and analysis (reviewing focus groups transcripts ‘line-by-line with an academic researcher); 
  • Training new academic researchers in delivering interview schedules; 
  • Intervention theory development; 
  • Dissemination. 
Engager 2 montage

Engager Peer Researcher film

A video telling the story of what it meant to the Peer Researchers to be involved in Engager, and the advice they would give to someone else considering being involved in a research project.

Summary of the Engager intervention

As of February 2020, there were over 83,000 people incarcerated in England and Wales, the majority (95%) were male. A large proportion have mental health problems and co-morbidity, including substance misuse, is the norm, along with homelessness, unemployment and broken relationships. The risk of suicide for men leaving prison is eight times the national average. 
Prison mental health services for those with severe mental illness has improved. In contrast, identification of common mental health problems is haphazard and few access community services. No systems worldwide have been identified for engaging people with common mental health problems while in prison, providing support and working with them to engage with community services. 
For ENGAGER, where a substantive intervention did not exist, we used a realist review (Pearson et al., 2015), alongside case studies, focus groups and discussion with an expert stakeholder group, including peer researchers, to produce an initial programme theory. We also incorporated extant behaviour change theory, selected according to context, which 5 proposed both how practitioners should work with offenders and how implementation should be achieved in the form of an implementation delivery platform (i.e. practitioner manual, training, and supervision). The initial ENGAGER programme theory describes how change was intended to occur for whom and in what circumstances in the intervention.
Please contact primarycare@plymouth.ac.uk to request a copy of the manual or gain advice from the research team on developing services based on the Engager model.

The South West team

Engager team

The Northwest team:

Professor Jenny Shaw, University of Manchester 
Principal Investigator – Northwest Site

Dr Charlotte Lennox, University of Manchester
Senior Research Fellow; Project Manager for Northwest site

Caroline Stevenson, University of Manchester
Research Assistant

 If you wish to find out more please contact us at primarycare@plymouth.ac.uk or +44 1752 764230.

Collaborators: Exeter University

Health Economics: 

Statistics and Trial Design:

Realist Review:

Qualitative Methodology:

Collaborators: other institutions

Professor Susan Michie
Director, UCL Centre for Behaviour Change

Dr Nat Wright
Associate Medical Director Specialist Services and Vulnerable Groups
Leeds Community Healthcare

Professor Mike Maguire
Professor in Criminology
University of South Wales

Dr Alex Stirzaker
IAPT Advisor and Specialist in PD and SMI
Avon & Wiltshire Mental Health Partnership NHS Trust

Dr Mark Haddad
Senior Lecturer in Mental Health
City University London

Dr Graham Durcan
Associate Director, Criminal Justice
Centre for Mental Health 

Rachael Hunter​
Senior Research Associate

Dr Christine Brown
Consultant Forensic Psychiatrist 
Devon Partnership Trust

Dr Tirril Harris
Former Senior Research Fellow
King’s College London.

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