Guest editorial: The need for improved dual diagnosis research in criminalised populations

Criminalised persons are amongst the most disadvantaged people in society, with rates of chronic diseases, mental health and substance use comorbidity far greater than the general population (Health of prisoners, 2022). Among criminalised populations, there is an over-representation of individuals with co-occurring mental illness and substance dependence, also commonly termed a dual diagnosis. Globally, around one quarter of people in custody are estimated to have a dual diagnosis (Taggart et al., 2025) with this prevalence being two to 20 times higher than in the general population (Baranyi et al., 2022). However, a recent study using multiple data sources estimated the prevalence of dual diagnosis being seen in up to 44.2% of a prison population in Australian prisons (Coulter et al., 2025).Criminalised persons with dual diagnosis are highly vulnerable to experiencing a range of adverse outcomes. The first week post-release from custody is associated with the highest risk of death, with alcohol and other drug overdose and suicide being the two largest causes of death (Borschmann et al., 2024). Compared to individuals without dual diagnosis, individuals released from prison who have a dual diagnosis experience an increased risk of injury (Young et al., 2018), drug overdose (Keen et al., 2020) and emergency department attendances (Butler et al., 2020). Additionally, dual diagnosis is associated with significantly higher costs across both the health care and criminal justice systems (Snow et al., 2022).Despite the high burden of dual diagnosis among criminalised populations, research addressing this topic, is scarce (Moyes et al., 2016). The article by Grummitt et al. 2025 in this journal issue “Post-traumatic stress disorder and hazardous alcohol use among incarcerated adults: associations with criminogenic needs and reoffending in New South Wales, Australia” adds to this literature base. There is an urgent and apparent need to improve treatment outcomes and interventions within this population as part of a rehabilitative and therapeutic approach. Research has shown that promising, cost-effective, practical and beneficial treatments are available for criminalised individuals with dual diagnoses across various settings, including integrated residential programs (Majer et al., 2016) and community treatment programs (Smelson et al., 2020). Despite this, gaps in knowledge still exist and further research is needed.Research within correctional settings is notoriously difficult to conduct (Cislo and Trestman, 2013). There are several key factors highlighted by researchers to account for these challenges, including the complex, multi-tiered requirements of ethics committee reviews; inconsistencies in determinations across different ethics committees; a lack of support for research activities by correctional authorities; and limited research expertise among individuals involved in the review and approval processes for research (Charles et al., 2016; Simpson et al., 2017; Simpson et al., 2025). Yet, there is a pressing need for this work, Hoang et al., 2025 in this special edition highlight in “Substance Use Disorders and Unauthorized Drug Use in an Australian Forensic Mental Health Hospital” highlight the scale of dual diagnosis in correctional health facilities. These factors need to be balanced against the inherent vulnerability of criminalised people when conducting research, acknowledging the lack of autonomy in a correctional environment, and historical research abuse against criminalised people (Brewer-Smyth, 2008; Pont, 2008). There is a need for increased ethical oversight and consideration given the power imbalance between researchers and criminalised individuals and the associated risks of coercion, exploitation and experience of stigma.Research involving criminalised populations involves a wide range of stakeholders, including correctional authorities, contracted service providers and correctional officers. Many forensic institutions and organisations are government-operated, meaning that research often requires approval from correctional authorities. This may lead to delays and barriers to the research approvals process. Increasing privatisation of custodial facilities further complicates this landscape. The outsourcing of treatment to external providers, often governed by opaque contracts, with limited public accountability (Anaf et al., 2024) can introduce additional stakeholders and layers to the ethics approval process, including multi-centre ethics and research review processes. Across both public and private settings, stakeholders may have differing priorities and concerns, including perceived reputational risk to correctional organisations, particularly if findings highlight deficiencies or shortcomings in current practice. While such concerns can create barriers to approval, they also underscore the need for robust, transparent research to improve outcomes. Regarding dual diagnosis in particular, Zhou et al.’s 2025 systematic review in this edition, “A review of clinical staff attitudes, perceptions and knowledge regarding substance use and its treatment in the forensic setting” highlighted the challenges of managing people with dual diagnosis in correctional settings due to several factors including security and operational constraints, staff training and knowledge gaps and stigma. The paper further emphasises that only by rectifying these factors can service and treatment provision improve.The challenges in conducting research with criminalised populations are problematic on several fronts. Robust research processes, including reporting and publication, are needed to support evidence-based improvements to healthcare delivery and ensure healthcare disparities are being addressed. Furthermore, the unique profile and legal situation of this population mean that extrapolation of research findings may not be appropriate. For example, initiation of opioid agonist treatment before release may be more beneficial than for similar individuals in the community due to the high risk of overdose during the post-release period (Borschmann et al., 2024). We also contend that unnecessary barriers to research in the custodial settings contravene the United Nations Standard Minimum Rules for the Treatment of Prisoners (the “Mandela Rules”). The “Mandela Rules” stipulate that people who are incarcerated are due the same standards of health care as are equivalent in the community (United Nations Office on Drugs and Crime, 2015) and should also be afforded the same opportunities to be engaged and represented in research aimed at improving the quality of care provided.There is mounting consensus about the importance of lived experience expertise in health research; however, lived experience involvement in custodial research is rare (Simpson et al., 2021). There is also increasing evidence that the increased utilisation of people with lived experience to research teams leads to increased research relevance, improvements in participant recruitment and retention, more effective dissemination and translation of research findings, and increased diversity within the research team (Anderst et al., 2020). In this edition, Lean et al., 2025, in their article ‘‘Worse Than When They Came In’: Dual Diagnosis, Prison Health Neglect, and the Structured Violence of Denied Care’; provide a unique and well-articulated insight into the provision, or lack thereof, of appropriate dual diagnosis care in custodial environments. Through a lens of lived experience and an abolitionist framework, they argue that such care cannot be effectively delivered in correctional settings. These perspectives are challenging but important and need to be part of the national discourse on how criminalised people are treated and their needs addressed.To address the issues highlighted above, we propose the following measures:The current state of research on dual diagnosis among criminalised populations is untenable. The challenges to conducting rigorous research render the ability to monitor, review and improve care for people with dual diagnosis nearly impossible. This increases the risks of perpetuating policies that can be detrimental and harmful to criminalised people and for those with dual diagnosis, the risk of under recognition and suboptimal management of their mental health and substance use disorders and the harms associated with this. The measures outlined above could serve as the first step in rectifying these issues.This project was self-funded with no external funding obtained.Thileepan Naren has received speaking honoraria, conference and travel support from Camurus.