Critical time intervention to prevent homelessness and improve health for people leaving prison: the PHaCT pilot RCT

Background
People leaving prison face significant barriers to reintegration, often resulting in homelessness, which exacerbates health issues and increases recidivism. Critical time interventions aim to support vulnerable individuals during significant life transitions by providing time-limited, emotional and practical support. While effective in other contexts, the impact of housing-led critical time interventions for people leaving prison in the United Kingdom remains unclear. The PHaCT study was a pilot randomised controlled trial of a housing-led critical time intervention for people leaving prison at risk of homelessness. This study aimed to determine whether a full-scale randomised controlled trial of the critical time intervention model in prison leavers at risk of homelessness was feasible

Methods
The pilot was a parallel two-arm, individual-level randomised controlled trial of a pre-existing critical time intervention intervention with an integrated process evaluation and embedded exploratory health economic evaluation. Recruitment occurred in fours male prisons across England and Wales with participants followed up in the communities. Prisons were randomised by site to either receive the critical time intervention or receive usual support, and participants were recruited within 12 weeks of their release. The locations were predetermined by where the intervention was already being delivered by the intervention provider (critical time intervention teams). Critical time intervention included pre-engagement, transition to community, try-out and transfer of care phases, each lasting 3 months. Data collection methods included baseline surveys, follow-up assessments at 3, 6 and 9 months, qualitative interviews, and session observations. Routine data linkage was explored separately to assess feasibility. Progression criteria included recruitment, retention, process evaluation and fidelity.

Results
Thirty-four male participants (mean age 38 years) were recruited, with 19 assigned to the intervention and 15 to control. The study achieved a high recruitment rate of 92%, but retention was a significant challenge, with only 18% of participants retained at 9 months follow-up. The process evaluation found critical time intervention was acceptable to staff and participants, but ethical concerns around randomisation and informed consent were raised. Fidelity to the critical time intervention model was generally high, though contextual instability in housing and criminal justice systems posed challenges. Data collection methods for health economics and data linkage were feasible and acceptable.

Limitations
The approval to access prisons was lengthy and support provided by Clinical Research Networks was delayed. Contextual instability within the housing and criminal justice systems, including a lack of social housing, high recall rates, the removal of the requirement to have a probation officer and the emergency early release of people in prison, further complicated the trial. Ethical concerns around randomisation and informed consent affected trial acceptability.

Conclusions
The trial methodology faced significant challenges. Low retention rates, ethical concerns by intervention delivery staff around randomisation and contextual instability suggest that a full-scale randomised controlled trial is not feasible.

Implications/future work
The findings highlight the need for systemic changes within the research support provided to prison-based studies, housing and criminal justice systems to support research in prisons and interventions for people leaving prison. Decision-makers should prioritise policies that increase the availability of affordable housing and provide post-release support. Future research should explore alternative study designs and more intensive recruitment and retention strategies.

Funding
This synopsis presents independent research funded by the National Institute for Health and Care Research (NIHR) Public Health Research programme as award number NIHR134281.