Young people with better aerobic fitness may have a lower risk of developing depression later in life, according to an Australian study that tracked participants for more than three decades.
Researchers analysed data from more than 1,000 people who were part of a nationwide Australian cohort first surveyed in 1985. Participants were followed for 34 years, with their mental health monitored through diagnostic interviews.
The researchers assessed physical fitness during childhood using several tests. These included a 1.6-kilometre run to measure cardiorespiratory fitness and a standing long jump to assess muscular power. A smaller group also completed cycling and handgrip strength tests.
The study, published in the Journal of Affective Disorders, found that participants who completed the running test faster had a 15% lower relative risk of developing depression in adulthood.
The average time for the 1.6-kilometre run was about eight minutes and 27 seconds. Those who ran around one minute and 15 seconds faster than the average were associated with the lower risk of depression later in life.
The researchers found that the strongest association between cardiorespiratory fitness and reduced depression risk occurred five to 10 years after the initial fitness assessments, when participants were still relatively close to childhood.
Although the protective association weakened over time, it remained detectable throughout the full 34-year follow-up period.
The study also found differences between men and women. Across the cardiorespiratory fitness measures, the association between higher fitness and lower depression risk was consistently stronger among females. Women in the study were also more likely than men to experience depression during their lives.
The researchers cautioned that the findings do not establish that poor fitness during childhood directly causes depression in adulthood. Depression has multiple contributing factors, including biological, social and environmental influences.
Kyle Smith, the study’s lead author, said childhood fitness could have benefits that extend beyond physical health.
“While we cannot say a lack of fitness during childhood causes depression in adults, the findings suggest that childhood fitness may have benefits beyond physical health,” Smith said.
He added that fitness was likely to be only one factor among many affecting a person’s risk of depression.
The findings come as rates of mental health conditions continue to rise globally. About 322 million adults worldwide, or roughly one in 20 people, live with depression, according to estimates cited in the report.
Researchers are increasingly examining lifestyle factors that could help prevent or delay mental health conditions as depression and anxiety become more widespread.
Grant Tomkinson, a researcher at the University of Adelaide, said physical fitness was particularly important because it could be improved through changes in lifestyle.
“Importantly, fitness is something we can change; it may be an important target for improving long-term mental health,” Tomkinson said.
The researchers said further studies are needed to understand how physical fitness during childhood may influence mental health decades later.
