More daily steps in early adolescence linked to fewer mental health problems a year later

A study of more than 5,500 US adolescents found that those taking at least 8,000 steps a day reported fewer emotional and behavioural difficulties one year later, although the observational findings do not prove that walking prevents mental health problems.

A large US cohort study published in JAMA Network Open has found that adolescents who take more daily steps tend to report fewer mental health problems a year later, adding to evidence that everyday movement may matter for emotional wellbeing as well as physical health. The researchers, led by teams at King’s College London and the University of Massachusetts Amherst, analysed data from 5,515 children taking part in the Adolescent Brain Cognitive Development study, one of the largest long-term studies of brain development in the United States.

The participants were about 11.9 years old on average and came from 21 research centres across the country. They wore Fitbit devices for roughly three weeks between November 2018 and November 2020, giving the team an objective measure of daily step counts rather than relying on self-reporting. One year later, the researchers used child behaviour checklists completed by both adolescents and their parents to assess anxiety, low mood and behavioural difficulties.

The pattern was straightforward: teenagers logging fewer than 5,000 steps a day had the highest level of mental health problems, those averaging around 8,000 steps fared better, and those reaching 12,000 steps or more had the fewest reported difficulties. Within the range observed, the association did not appear to flatten out, although the number of highly active participants was small, so the study could not establish whether the trend would continue at even higher activity levels. The researchers also found no meaningful link between step counts and academic performance.

Brain scans suggested a possible explanation, but not a definitive one. The study found small differences in cortical thickness in areas including the postcentral gyrus, which is involved in sensory processing, and the anterior cingulate cortex, which helps with emotion and information processing. Statistical analysis indicated that changes in the postcentral gyrus partly explained the association between higher step counts and fewer later mental health problems. Even so, the authors stressed that the differences were modest and that the findings do not prove that walking alters brain development or directly prevents mental health symptoms.

The study did take earlier mental health into account, and the link between more steps and better later outcomes remained. But because it was observational, it cannot rule out reverse causation: adolescents who were already doing better psychologically may simply have been more active to begin with. The team said routine activities such as walking to school, playing outdoors and other forms of regular movement deserve further study, but the results should be read as a statistical association rather than a treatment recommendation.