Which factors mediate the effect of childhood socioeconomic disadvantage on mental health in young adulthood? A protocol for a target trial emulation using linked administrative data from New South Wales, Australia.
This paper presents a protocol for a target trial emulation using linked administrative data from New South Wales, Australia (1990-2022) to examine how multiple mediating pathways explain the relationship between childhood socioeconomic disadvantage and acute mental health admissions and presentations in young adulthood.
Key Findings
Background
Early-life socioeconomic status increases the risk of poor mental health outcomes in adulthood, but the mechanistic pathways underlying this relationship remain poorly understood.
The study protocol acknowledges a well-established association between early-life SES and adult mental health outcomes.
The authors state that 'the mechanistic pathways underlying this relationship remain poorly understood.'
Identifying specific mediating pathways is framed as revealing 'more immediate opportunities for effective interventions' while broader socioeconomic change remains a long-term goal.
Methods
The study will use linked administrative data from New South Wales, Australia covering the period 1990 to 2022 to emulate a target trial.
The data linkage spans a 32-year period (1990-2022).
The study is based in New South Wales, Australia.
The target trial emulation framework will be used to examine the relationship between SES at birth and mental health outcomes.
Ethics approval was received from the University of Newcastle (H-2024-0015) and Aboriginal Health and Medical Research Council (2265/24).
Methods
The primary exposure is socioeconomic status at birth and the primary outcomes are acute mental health admissions and presentations between ages 18 and 25 years.
SES is measured at birth as the exposure variable.
Outcomes are specifically defined as acute mental health admissions and presentations.
The outcome measurement window is restricted to young adulthood, ages 18 to 25 years.
Methods
The study will examine five specific mediating pathways between childhood socioeconomic disadvantage and young adult mental health outcomes.
The five mediators are: education, housing stability, child protection contact, parental incarceration, and justice system involvement.
An interventional mediation analysis approach will be used to examine these multiple mediating pathways simultaneously.
The analysis will estimate 'direct and indirect interventional effects, quantifying how much of the SES-mental health relationship could be modified by interventions on specific mediators.'
Methods
The study will use an interventional mediation analysis framework to estimate how much of the SES-mental health relationship could be modified by targeting specific mediators.
Both direct and indirect interventional effects will be estimated.
The approach quantifies the proportion of the SES-mental health relationship attributable to each specific mediating pathway.
This analytical approach is designed to translate findings into actionable intervention targets.
Methods
Dissemination of findings will include targeted communication to government agencies and policymakers through policy briefs and stakeholder meetings.
All dissemination activities will be conducted in accordance with data access agreements and following approval from all relevant data custodians (New South Wales Health System Data Services).
Key findings will be communicated to relevant government agencies and policymakers through policy briefs and stakeholder meetings.
Findings will also be published in appropriate academic journals.
What This Means
This research describes a planned study that will investigate why children who grow up in poverty are more likely to experience serious mental health problems as young adults. Using administrative records from New South Wales, Australia spanning over three decades (1990-2022), the researchers will track individuals from birth through to early adulthood (ages 18-25) to understand which life experiences along the way help explain this connection between childhood poverty and later mental health crises. Rather than simply confirming that poverty and mental health problems are linked, this study aims to identify the specific pathways — such as dropping out of school, unstable housing, involvement with child protective services, having a parent sent to prison, or getting caught up in the justice system — that carry that risk forward through life.
This research suggests that by identifying these specific pathways, it may be possible to design targeted interventions that could reduce mental health inequalities even before broader socioeconomic inequalities are addressed. For example, if housing instability emerges as a key pathway, programs that help low-income families maintain stable housing during childhood could potentially reduce mental health admissions in young adulthood. The analytical method being used (interventional mediation analysis) is specifically designed to estimate how much of the mental health gap between socioeconomic groups could be closed if one or more of these specific pathways were successfully interrupted by a well-designed intervention.
This is a protocol paper, meaning the researchers are publishing their detailed plan before conducting the analysis, which is a practice that increases scientific transparency and accountability. No results are yet available, but the findings — when complete — are intended to be shared directly with government agencies and policymakers in Australia, with the goal of informing practical policy decisions about how to reduce mental health inequalities among young people from disadvantaged backgrounds.
Leigh L, Hinwood M, Oldmeadow C, Bryant J, Heard T, Fakes K, et al.. (2026). Which factors mediate the effect of childhood socioeconomic disadvantage on mental health in young adulthood? A protocol for a target trial emulation using linked administrative data from New South Wales, Australia.. BMJ open. https://doi.org/10.1136/bmjopen-2025-109541