Researchers found that people who undertook vigorous or moderate exercise were less likely to develop mental health conditions such as anxiety or depression
"This is a very strong public health message, as exercise is free, and everyone can increase how much they do in a week.” Dr Carlos Celis-Morales, doctor of public health, University of Glasgow
Regular workouts could prevent anxiety and depression in a a quarter of people, a new study suggests.
The University of Glasgow study, published in BMC Medicine, looked at 37,000 people from UK Biobank aged 37 to 73, none of whom had any previous diagnosis of depression or anxiety. All participants were given fitness trackers, worn on the wrist, to monitor physical activity. When they were followed up seven years later, 3.4% had developed an affective disorder such as depression or anxiety.
Replacing 30 min of sedentary behaviour in a week with either moderate or vigorous physical activity was associated with a lower risk of affective disorders, the research found. Assuming a causal relationship, the researchers suggest that 5% of affective disorders could be prevented by at least 150 minutes of moderate physical activity a week, and 19% could be prevented by at least 75 minutes of vigorous physical activity a week.
The UK Biobank cohort study recruited 500,000 people between 2006 and 2010. They all completed a touch-screen questionnaire, had physical measurements taken, and provided blood, urine, and saliva samples at baseline. In the case of the 37,000 people taking part in the Glasgow study, researchers also had access to their electronic health records.
The study found that participants who undertook more physical exercise were on the whole younger, less deprived, more likely to be female and white, less likely to smoke, and consumed more fruit and vegetables and less red and processed meat. They also had lower BMIs and were less likely to have longstanding illnesses. However, the study found that physical exercise was associated with lower risk of anxiety and depression even when adjusting for sociodemographic and lifestyle.
Dr Carlos Celis-Morales, senior author of the study and doctor of public health at the University of Glasgow, said: “This is a very strong public health message, as exercise is free, and everyone can increase how much they do in a week.”
One of the strengths of the study, researchers said, was that it used device-measured physical activity, which is less prone to measurement errors and free of self-reporting bias than questionnaires. Another is that it drew information about mental health diagnoses from multiple electronic health records, improving data completeness and protecting against reporting bias.
However, the researchers also noted limitations. The UK Biobank is not representative of the population, and there is “evidence of a healthy volunteer selection bias.” They note too that “participants with worse mental health might not be recruited or willing to participate from the accelerometer measurements.” It is not possible to be sure, they add, of a causal relationship between exercise and better mental health outcomes.
This is not the first study to suggest that that exercise might boost mental health, but the large size of the cohort, and the use of electronic fitness trackers rather than reliance on self-reporting, gives weight to its findings. We always have to be cautious, however, about deducing causation – it’s possible that people who are already less susceptible to mental illness are more likely to exercise. If there is a causal relationship, we can’t be sure whether the benefit comes from the exercise itself or other factors such as being outdoors or socialising with other people. Nonetheless, the findings are encouraging, and should pave the way for further research and adoption over the longer term.