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Project Collaborators External

• Dr Michael Doyle, Associate Professor Jack Stone, Mr Joe Coyte, Dr Mary Ellen Harrod, Mr Luke Grant, Ms Gloria Larman, Professor Peter Vickerman, Ms Colette McGrath, Dr Peter Thompson, Ms Alison ChurchillÌý

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Project overview

People who have been incarcerated face significant health and social challenges after leaving prison, particularly related to serious mental illness and drug dependence. These challenges are especially pronounced among women and First Nations people. There is an urgent need to understand which interventions can most effectively mitigate these risks and improve outcomes for these marginalised groups. This data linkage includes all people incarcerated in NSW since 2000 (~200,000 people), linked to 16 NSW and national datasets. These data include information on crime, health service utilisation, infectious disease notifications, alcohol and other drug treatment, mental health treatment, social services, and mortality.ÌýÌý

By integrating and analysing this comprehensive data, we aim to:ÌýÌý

1. quantify the most significant adverse health and social outcomes, such as mortality (including suicide and drugrelated deaths), hospitalisations, emergency department visits (psychiatric, overdose-related, and blood-borne virus-related), and recidivism;Ìý
2. evaluate the effectiveness of existing mental health and drug dependence treatment in improving outcomes; and
3. mathematically model which interventions are likely to have the largest impact when scaled to a population level. Throughout each of these aims, we will conduct specific analyses focusing on women and First Nations people.Ìý

By addressing these issues, our study will address the inequities in health and social outcomes for this marginalised population and drive systematic changes that significantly improve the lives of people released from incarceration.Ìý

Design and Method

This is a population-based retrospective cohort of all adults (18+ years) incarcerated in NSW since 1 January 2000, an estimated ~200,000 people. The study links data from 16 datasets capturing engagement with the criminal justice system, health service utilisation, disease notifications, alcohol and other drug treatment, mental health treatment, social services and mortality.ÌýÌý

Data linkage is being conducted by the Centre for Health Record Linkage Data Linkage (CheReL) Unit (for NSW Health and Corrections NSW datasets) and the Australian Institute of Health and Welfare Data Integration Unit (for national data). All data for analysis will be stored in the Secure Unified Research Environment (SURE), a high-security data environment for health research approved by all custodians for the datasets being linked for this project. Researchers will access only de-identified data via SURE. Access is restricted to researchers listed on ethical approvals, ensuring data integrity and confidentiality.Ìý

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Aim 1: Quantify adverse health and social events post-release

We will quantify rates of adverse health and social events among people released from incarceration for the study follow-up time (or until re-incarceration or death) and at different time periods (1, 3, 6, 12 and 24 months post-release), with confidence intervals derived from a Poisson or negative binomial distribution as appropriate. We will test for differences in these outcomes among specific subgroups, including individuals with histories of serious mental illness, opioid dependence, methamphetamine dependence, women and First Nations people.

We will calculate effect estimates (e.g., hazard ratios, odds ratios, incidence rate ratios) to assess heterogeneity between population subgroups descriptively, by constructing models within each subgroup, and formally through hypothesis testing of interaction terms. Analyses will be stratified by duration of incarceration, consider each adverse outcome separately and be adjusted for relevant confounders. We will also investigate the effect of repeat incarceration episodes and calculate median time to health and social outcomes from release of incarceration. Subgroup analyses will focus on individuals with histories of opioid/methamphetamine dependence or serious mental illness; we will examine potential differences in outcomes for women and First Nations people.

Aim 2: Assess the effect of interventions to reduce adverse health and social events among select subpopulations

The overall objective of this aim is to assess the impact of interventions on the risk of adverse health and social outcomes. We will examine interventions provided to three distinct subpopulations - people with opioid dependence, methamphetamine dependence and serious mental illness. For people with a history of each disorder, we will investigate the time taken to obtain disorder-specific treatment in the community, censoring at end of follow-up, death, or reincarceration. We will test for variations in exposure and treatment effects between women and men, and between First Nations and non-First Nations people using similar approaches described in Aim 1.

Sub-Aim 2.1: Opioid agonist treatment (OAT) for people with opioid dependence

This sub-aim extends our previous work on receipt of OAT post-release to other outcomes. We will identify people with opioid dependence who (i) received OAT while incarcerated, (ii) were linked with OAT in the community, defined as initiation within 7 days of being released, and (iii) define periods of time on and off treatment in the post-release period. Using similar statistical methods outlined in Aim 1, we will use models to separately examine the adjusted association between health and social outcomes and treatment status (in/out of OAT). Treatment status will be defined as a time-varying variable, and effects estimated over the post-release period and by different time periods post release (1, 3, 6, 12 and 24 months).

Sub-Aim 2.2: Interventions for methamphetamine dependence

The method in Aim 2.1 will be extended to examine methamphetamine dependence interventions using AODTS data: counselling, support, case management, residential rehabilitation.

Sub-Aim 2.3: Interventions for serious mental illness

Treatment will be defined based on clinical services recorded under the Medicare Benefits Schedule (e.g. psychiatrist or psychologist); medications (e.g. antipsychotics) prescribed and recorded in the PBS; and mental health outpatient visits (MH-AMB). For medications we will estimate periods in and out of treatment, using our work operationalising opioid exposure using PBS data in previous studies. The methodology in Aim 2.1 will be extended to estimate the effect of treatment receipt on health and social outcomes, comparing periods of time in and out of treatment.

Sub-Aim 2.4: Target trial emulation comparing methadone versus long-acting injectable buprenorphine (LAIB) for people with opioid dependence post-release

We will apply a target trial framework to emulate the design and analysis of a randomised control trial to examine the impact of LAIB compared to methadone on health and social outcomes following prison release. Using a target trial design avoids biases that can be present in observational studies. This emulated target trial will also demonstrate utility for future application to other interventions.

We will standardise the time for study onset (time zero) and apply relevant exclusion criteria. Eligibility may be met at multiple times within our data resulting in nested trials requiring the appropriate adjustment to the variance estimator. Both intention-to-treat (ITT) and per protocol (PP) causal contrasts will be estimated. We will build three separate outcome models to compare methadone and LAIB on retention in treatment and two adverse events (fatal overdose, mortality). The risk of each adverse event will be estimated at 1, 3, 6, 12, 24 months. A logistic model will be built to predict being prescribed LAIB based on a history of previous treatment and drug use.

Aim 3: Modelling the population-level impact of scaling up interventions post-release

We will use mathematical modelling to project the population-level impacts of scaling up mental health, opioid and methamphetamine dependence interventions post-release. We will assess past interventions and estimate the potential reduction in adverse outcomes by scaling up linkage to care upon release. We will assess past and future impact by sex and First Nations status.

Progress/Update

POST has all required ethics approvals: NSW Population and Health Services Ethics Committee (No: 2022/ETH00289), Australian Institute of Health and Welfare (No: EO2022/5/1371), Corrections Health (No: 2021.61), Aboriginal Health and Medical Research Council Ethics Committee (No: 1999/22), and аIJʹÙÍø Sydney Human Research Ethics Committee (No: iRECS6272). A waiver of consent has been granted through ethics approval.

NSW data linkage has been conducted by the Centre for Health Record Linkage Data Linkage (CheReL) Unit (for NSW Health and Corrections NSW datasets). NSW data has been received from NSW data custodians and cleaning and analysis has commenced. National data linkage is currently in progress with the Australian Institute of Health and Welfare (AIHW) Data Integration Unit.

This project was the successful recipient of a NHMRC Clinical Trials and Cohort Studies Grant, with funding to start 1 July 2025.

Benefits

While studies have documented the elevated risk of communicable diseases and mortality in prisoners post-release, most health and social outcomes remain under-researched and there is a lack of population-wide research on health and social outcomes post-release from incarceration. Individuals with serious mental illness or drug dependence, women and First Nations people face unique challenges and health disparities that are not adequately addressed by general population studies. Despite this, research on these subpopulations among people who are incarcerated is limited: evidence to drive change and improve outcomes is critically needed.

Through the use of a population-wide linked cohort we will be able to generate evidence on the risk of harms post-release from incarceration, including among key subpopulations, highlighting the magnitude of the risks that people leaving incarceration face. But importantly, we will also generate – in this instance, through the examination of effects of receiving mental health and drug dependence treatment – the benefits of linkage to care post release. The extension of this through development of a mathematical model to demonstrate expected impacts of improving linkage to care post-release will be an important advocacy tool for people with lived experience, community groups and policymakers.

This work will quantify outcomes and generate evidence around critical points for intervention to reduce health and social harms among people released from incarceration, informing Justice Health, Corrective Services and community agencies. It will also answer policy-relevant questions about the impact of improving the transition from incarceration to community care; and additionally, the benefits of increasing programmes that divert people from incarceration.