Australia's 100,000-Person Study Targets Mental Health and Early 2026

Australia's largest intergenerational study of wellbeing and ageing, the 18 and Up study, aims to uncover the drivers of mental health disorders and rising early-onset cancer rates among younger generations. Launched by the Sax Institute on Thursday, the study will recruit 100,000 Australians aged 18 to 45 and follow their health throughout their lives.

The independent, not-for-profit research institute hopes to fill a critical gap in long-term data for younger people. Two decades ago, the same institute began the 45 and Up study, now the largest population-based cohort study in the southern hemisphere, with more than 267,000 participants.

Why the 18 and Up Study Matters for Younger Australians

Existing health studies often provide only a snapshot in time, leaving researchers without the long-term evidence needed to understand how mental illness and cancer develop over a lifetime. The 18 and Up study seeks to change that by tracking participants' health trajectories from early adulthood onward.

Adjunct Prof Justine Gatt, scientific director of 18 and Up and a neuroscientist, noted that almost two in five young Australians aged 16 to 24 experienced a mental disorder in the past year, and that number has been rising. "Yet we still lack the long-term evidence needed to understand why," she said.

How the Study Builds on the 45 and Up Success

The 45 and Up study has already led to significant discoveries about smoking, dementia prevention, and differences in cardiovascular outcomes between men and women. Participants have been repeatedly surveyed, and their responses linked to other datasets, creating a rich resource for researchers.

By extending this model to a younger cohort, the Sax Institute expects to generate insights into the early origins of chronic diseases and mental health conditions. The study will follow participants aged 18 to 45 throughout their lives, capturing changes in health behaviours, environments, and outcomes.

Key Takeaways from the 18 and Up Launch

• The Sax Institute has launched the 18 and Up study, aiming to recruit 100,000 Australians aged 18 to 45.
• The study will track participants' health over their lifetimes to identify causes of mental health disorders and early-onset cancer.
• It builds on the 45 and Up study, which has over 267,000 participants and has produced major findings on smoking, dementia, and cardiovascular health.
• Nearly two in five young Australians aged 16 to 24 experienced a mental disorder in the past year, a rising trend that lacks long-term explanation.
• The research is independent and not-for-profit, with a focus on generating evidence to improve public health.

What the Study Will Investigate

The 18 and Up study will collect data on a wide range of factors that influence health, including mental wellbeing, lifestyle behaviours, and environmental exposures. Researchers will link survey responses to other datasets, such as health records, to build a comprehensive picture of participants' health over time.

This approach allows scientists to examine how early-life experiences and behaviours contribute to conditions like depression, anxiety, and cancer. The study's longitudinal design means it can identify risk factors and protective factors that might be missed in shorter-term research.

Comparing Australia's Major Cohort Studies

Implications for Public Health and Policy

The findings from 18 and Up could inform prevention strategies and health policies aimed at younger Australians. With mental health disorders and early-onset cancers on the rise, understanding their root causes is essential for developing effective interventions.

The study's scale and duration will provide robust evidence to guide clinical practice and public health messaging. As the cohort ages, researchers will be able to observe how health outcomes unfold and identify opportunities for early intervention.

How to Get Involved and What to Watch Next

Australians aged 18 to 45 are encouraged to consider participating in the 18 and Up study. Recruitment is underway, and participants will be asked to complete surveys and allow their data to be linked to health records.

For those concerned about early-onset cancer, understanding the rising incidence among younger generations is crucial. The early onset cancer rise: why younger generations face higher risk provides context on this troubling trend and the need for research like 18 and Up.

Mental health support systems are also under scrutiny, particularly for Australians with disabilities. Recent NDIS autism reforms: 145,000 Australians to lose support have raised concerns about access to care, highlighting the importance of evidence-based policy.

Similarly, proposed NDIS autism support cuts: 145,000 Australians to lose funding could affect vulnerable populations, underscoring the need for longitudinal data on mental health outcomes.

Financial pressures also impact wellbeing, as seen in how cash settlements on home insurance claims leave Australians facing uncertainty. Such stressors are relevant to the 18 and Up study's holistic approach.

For older Australians, conditions like hoarding disorder can complicate health management. The hoarding disorder support: breaking the stigma and finding help resource offers guidance, reflecting the intergenerational nature of many health challenges. The background to this story is set out in Australia's 100,000-Person Study Targets Mental Health and Early.