Childhood fitness linked to 13% lower risk of depression in later life

A 30-year Australian study of more than 1,000 people found that stronger cardiorespiratory fitness in childhood was associated with a lower likelihood of depression in adulthood, although it could not establish cause and effect.

A long-running Australian cohort study suggests that children and teenagers with better cardiorespiratory fitness may be less likely to develop depression later in life, adding to evidence that movement in youth may shape mental health well beyond the school years. Researchers from the University of Tasmania’s Menzies Institute for Medical Research and the University of Adelaide followed more than 1,000 Australians for over three decades and found that the strongest links to lower adult depression risk were tied to fitness levels developed through activities that raise the heart rate.

The study used data first collected in 1985 from children aged seven to 15, who completed a series of fitness assessments including a 1.6-kilometre run, a standing long jump and cycling tasks. The same participants were then re-evaluated as adults aged 36 to 49, when they took part in a mental health interview based on World Health Organization standards. According to the universities, the researchers observed that higher cardiorespiratory fitness in childhood and adolescence was associated with a reduced likelihood of depression in adulthood, with the clearest and most consistent pattern seen for aerobic fitness rather than muscular measures.

Brooklyn Fraser, a research fellow at the University of Tasmania and a co-author of the study, said each standard deviation increase in childhood and adolescent cardiorespiratory fitness, measured by running speed over 1.6 kilometres, was linked with a 13% lower risk of adult depression. Fraser said the findings suggest that fitness in childhood may have benefits extending well beyond physical health, but stressed that the work is observational and cannot prove cause and effect.

That caution is important. The researchers said the study can show an association, not that low childhood fitness directly causes depression decades later. Previous research has often relied on shorter follow-up periods or focused only on adults, which is one reason this analysis has drawn attention. The new paper, published in the Journal of Affective Disorders and listed on PubMed, also found that lower physical fitness was associated with depression both across adolescence and in adulthood, reinforcing the idea that physical health and mental health may travel together over time.

Experts quoted by Newsweek pointed to several possible explanations. Nicole Avena, a professor of neuroscience at the Icahn School of Medicine at Mount Sinai, said aerobic activity may help reduce chronic inflammation, a process often linked with depression, while also affecting stress hormones and increasing brain-derived neurotrophic factor, or BDNF, a protein involved in the survival and growth of nerve cells. Karmel Choi, a clinical psychologist at Harvard Medical School, said cardiorespiratory fitness may also act as a broad marker of overall health and may reflect social advantages such as safer places to play, organised sport and more stable living conditions.

Fraser said the findings strengthen the case for protecting physical activity in childhood and adolescence, including school sport and opportunities for both organised and informal play. She also noted that girls often drop out of exercise earlier than boys, making them a group worth particular attention. The researchers said more work is needed to identify the mechanisms behind the link and to test whether interventions that improve children’s fitness can later reduce depression risk. For now, the study suggests that fitness in the early years may be one potentially modifiable factor connected to long-term mental health.