Study of 100,000 Australians seeks causes of mental health disorders and early onset cancer

Researchers hope to better understand the drivers of major health challenges facing younger people, such as mental illness and rising cancer rates, through the recruitment of 100,000 people for Australia’s largest intergenerational study of wellbeing and ageing.

The independent and not-for-profit research institute the Sax Institute, on Thursday launched the 18 and Up study, which will follow the health of those aged 18 to 45 throughout their lives.

Two decades ago, the institute started 45 and Up, now the largest population-based cohort study in the southern hemisphere, with more than 267,000 participants ranging in age from 45 to older than 100.

Since then, participants have been repeatedly surveyed and their responses linked to other datasets, leading to significant discoveries about smoking, dementia prevention, and differences in cardiovascular outcomes between men and women.

18 and Up’s scientific director, Adjunct Prof Justine Gatt, said there was a lack of long-term data for younger generations, with existing studies often only giving researchers information from a snapshot in time.

“Almost two in five young Australians aged 16 to 24 experienced a mental disorder in the past year, and that number has been rising,” Gatt, a neuroscientist and mental health researcher said. “Yet we still lack the long-term evidence needed to understand why.”

Suicide is the leading cause of death among Australians aged 15 to 44, and researchers have said there is an urgent need to understand and address driving factors to improve prevention efforts and mental health treatments.

Children and grandchildren of 45 and Up participants will be invited to participate, which Gatt said will help researchers understand how health is influenced by a complex mix of family history, lived experiences and social conditions, and how these factors interact across generations.

The CEO of the Sax Institute, Dr Martin McNamara, said along with mental health, questions around cancer will also be an important part of the initial round of surveys.

Since 2000, there has been an increase in early-onset cancers – defined as those diagnosed beyond adolescence but before the age of 50 – in Australia and other parts of the world. This includes bowel, thyroid, breast and other cancers.

While scientists think increased screening, changing lifestyles and different exposures to risk factors in early life and young adulthood may all be factors, there have been calls for urgent research to better understand these and other influences.

Participants will be asked about health, lifestyle, social circumstances and background and, with consent, this information will be linked to other health records, such as cancer registries and Medicare.

“It’s important we follow people over time … so that we can figure out ways to fix and re-organise our health and care systems,” McNamara said.

“We’ll have a really good picture of their lives, the things that are important to them, their education, their employment, where they live.”

The study will evolve with participants to receive age-relevant questions, and emerging health conditions or pandemics will be factored in. It is being funded by a $4.5m National Health and Medical Research Council grant, with recruitment beginning in November.

Professor of epidemiology and public health at the Australia National University, Emily Banks, is a former scientific director at the Sax Institute who used 45 and Up study data to reveal in 2025 that smoking-related illnesses kill 66 Australians every day – more than previously thought.

Banks said large-scale cohort studies are powerful as they give researchers a window into the population and help detail what people are exposed to during their lives. She said the 45 and Up data has become an important collaborative resource.

It has been used by more than 800 researchers worldwide.

“We’ve had hundreds of researchers using the data. We also have around 10% of the population of New South Wales in that age [45+] group in the study,” she said.

“Some of the biggest advances in health have come from using this kind of information.”