Despite people with histories of incarceration and IDU typically exhibiting significant and complex health and social disadvantage [16, 19, 33] and exceptionally high rates of reincarceration [22], little is known about their experiences after release from prison. Our lack of understanding of individual, social and service access factors associated with patterns of drug use, health and criminogenic outcomes after release from prison impedes the development of effective policies and practices. The PATH Cohort Study purposively recruited people in prison for post-release follow-up who reported a history of regular IDU in the months immediately prior to incarceration and who were due for release within 12 weeks of interview. The PATH Cohort is unique in the Australian prisoner research context, where follow-up of prisoners has typically been much shorter [15, 34] or relied solely on secondary data linkage [9, 35]. The PATH Cohort is also unique in that it focuses on people who were injecting drugs regularly at the time of incarceration. This cohort represents a particularly complex and vulnerable group at high risk of a range of negative post-release outcomes. The detailed data collected at pre-release baseline, which we present in this paper, will couple with post-release follow-up data to provide unprecedented insights into the trajectories of this population over coming years to help inform pre- and post-release health and support programs.

The baseline characteristics of our cohort show expected indicators of socio-economic disadvantage, such as low educational attainment, accommodation instability and a reliance on government welfare and crime for income, and also an extensive history of incarceration that is reflected in community-recruited cohorts of PWID [31]. Our findings also show extensive patterns of intergenerational disadvantage. One quarter of respondents reported being removed from their parents as children, and almost half of participants who were parents or caregivers reported child protection involvement, and one in five reported having had their children removed from their care. While incarceration and intergenerational disadvantage has been extensively documented [36,37,38], the fact that almost two thirds of our cohort are the primary caregiver to a child underscores the substantial long-term social and economic costs associated with the nexus between disadvantage, dependent drug use and incarceration.

Substances reported as being injected by participants in the month prior to and during incarceration reflect recent trends in drug markets and drug-related harms in Australia and the emergence of methamphetamine as a commonly injected drug in Australia [2, 39]. In local Victorian drug trend surveillance, the proportion of PWID reporting methamphetamine as their most commonly injected drug increased from 17% in 2012 to 30% in 2016, although heroin remains the most commonly injected drug among survey respondents (66%) [40]. The over-representation of methamphetamine use in our cohort reflects other Australian law enforcement data on drug use among police arrestees [41, 42] and findings from a recent Australian study reporting methamphetamine as the most commonly injected drug prior to incarceration among prisoners with a history of IDU in New South Wales [43].

Among those who answered the question, almost two thirds of our sample reported ever injecting in prison (across a median of five previous incarcerations) and 40% reported injecting during their current sentence. While this prevalence of in-prison IDU is higher than other Australian studies, it is not unexpected given we purposively recruited participants frequently injecting prior to incarceration (at least monthly in the 6 months prior to incarceration) compared to others who recruited prisoners reporting any injecting in the 3 months pre-incarceration [42] or a lifetime history of injecting [23, 34]. The prevalence of pre-incarceration and in-prison methamphetamine injecting in our cohort, and trends in methamphetamine use among Australian PWID more broadly, highlights the need for effective methamphetamine treatment responses. Analysis of PWID cohort study data in Melbourne showed an association between drug first injected and current injecting drug preferences, and highlighted the need for flexible harm reduction and drug treatment services that respond to changing patterns of drug use [31]. This need for services that respond to changing drug use trends should also apply to law enforcement responses and programs available in prison. While OST is widely available in Victorian prisons (and was the most commonly accessed prison drug treatment program in our cohort), prison programs for methamphetamine dependence have relied primarily on group and individual counselling. While counselling treatment approaches to methamphetamine dependence have demonstrated some success in community settings [44], their effectiveness in prison settings is yet to be established [45]. A forthcoming trial of pharmacotherapy for the management of methamphetamine dependence [46] may result in new drug treatments suited to implementation in prison.

Our experience recruiting cohort participants provides insights into non-random and targeted prison recruitment strategies. Targeting recruitment to recent and frequent IDU meant that screening for eligibility via prison administrative data was not possible. Instead, we relied mostly on researchers spending extensive time in prisons and building trust and rapport with prisoners. Our recruitment strategies initially relied upon promoting the study via posters and program workers, but were soon modified to focus more on researchers’ direct engagement with prisoners in their units or at clinical or program visits. The ability to communicate the purpose of the study and answer questions about participation on the spot, and to encourage information about the study spreading via word-of-mouth, meant that direct engagement strategies were the most fruitful by far. In the context of aiming to recruit participants close to their expected release date, the most significant recruitment challenge was the transfer of eligible and interested prisoners out of recruitment prisons before scheduled interviews could take place. Movement between prison sites late in a sentence is also a challenge for the provision of effective transitional support for people leaving prison, particularly if transitional support service providers differ according to prison region or site.

Our study has limitations associated with sampling and reporting. First, as noted above, our eligibility criteria and limitations in administrative data meant that we were unable to implement a random sampling or consecutive sampling recruitment approach, and as such, findings may not be generalizable to the broader Victorian prison population with histories of IDU. More than twice the number of people recruited submitted an expression of interest form to participate in the study. While a small number were excluded from the study because they did not meet eligibility criteria (e.g. pre-incarceration drug use, release dates beyond the study recruitment period), inability to participate in the study mostly occurred because of transfers to other prisons prior to individuals becoming eligible to complete baseline surveys on the basis of expected release date. Movements between prisons overwhelmingly occur due to operational requirements rather than being based on prisoner behaviours or characteristics, and this inability to participate is therefore not expected to result in meaningful sampling bias. The restriction of the study to three recruitment sites and the variation in numbers recruited at each site may also introduce some recruitment bias. This paper is mostly based on self-reported responses and may be susceptible to reporting and recall bias, particularly for questions that refer to participants’ pre-incarceration experiences. However, for most survey domains, future record linkage will provide objective data to validate self-report and other measures (e.g. lifetime IDU history) that could not be collected in any other way. While our sample includes a higher proportion of Indigenous participants (17%) relative to the general Victorian prison population (7.8%) [12], it is unclear the extent to which this represents an over-representation of prisoners with IDU histories. The sample also includes participants with a median sentence length of 206 days. In Victoria, 25.8% of prisoners have an effective sentence length of less than 1 year. The shorter sentence length in our sample may reflect the types of crimes committed by people incarcerated for drug-related offences. Shorter sentences in this group bear further exploration in future analysis given access to some prison health programs (e.g. hepatitis C treatment) is restricted to those on longer sentences or residing in non-remand prisons. Finally, incarcerated women with IDU histories were not recruited and the study will therefore not reflect the experiences and specific challenges faced by women after release from prison [47]. The original study design included an over-sample of 100 female prisoners; however, operational pressures at the women’s prisons in Victoria precluded their recruitment (e.g. dealing with an influx of women prisoners and engaging in substantial new construction).

Our description of the baseline characteristics of PATH participants shows a cohort with substantial challenges with respect to physical and mental health, drug use, individual family histories, history of offending, educational attainment and employment history. Instability of accommodation and state involvement in the care of children further demonstrate the complexity of providing adequately coordinated, holistic care and support for this population during their reintegration into the community. Future analyses of prospective data will identify unmet community needs and describe the time-variant and time-invariant factors associated with specific health, drug use and criminogenic trajectories in this population. We aim to provide novel information to support policy and practice change related to the timing, targeting and modes of interventions designed to improve this population’s health and social outcomes.