Australia launches study of 100,000 people to find causes of youth mental illness and early-onset cancer

Australia's largest intergenerational study of wellbeing and ageing is being launched, with recruitment of 100,000 people under way. The independent, not-for-profit Sax Institute launched the '18 and Up' study on Thursday.

The study will follow people aged 18 to 45 throughout their lives. Researchers hope it will help them better understand the drivers of major health challenges facing younger people, including mental illness and rising cancer rates.

The study follows '45 and Up', started two decades ago. It is 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.

Participants in 45 and Up have been repeatedly surveyed and their responses linked to other datasets. That has led to significant findings about smoking, dementia prevention, and differences in cardiovascular outcomes between men and women.

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

Gatt, a neuroscientist and mental health researcher, said 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.

Researchers say suicide is the leading cause of death among Australians aged 15 to 44, and that there is an urgent need to understand the driving factors in order to improve prevention efforts and mental health treatments.

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

The chief executive of the Sax Institute, Dr Martin McNamara, said that alongside mental health, questions about cancer will also be an important part of the initial round of surveys.

Since 2000 there has been an increase in early-onset cancers in Australia and other parts of the world. These are cancers diagnosed beyond adolescence but before the age of 50, including bowel, thyroid and breast cancers.

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

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

McNamara said it was important to follow people over time 'so that we can figure out ways to fix and re-organise our health and care systems.' He said the study would give a full picture of participants' lives, including their education, employment and where they live.

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

Emily Banks, professor of epidemiology and public health at the Australian National University and a former scientific director at the Sax Institute, used 45 and Up 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 because they give researchers a window into the population, and more than 800 researchers worldwide have used the 45 and Up data.