A study of 1.2 million people has suggested that people who exercise regularly have, on average, 1.5 fewer days of poor mental health a month that those who do not exercise.
Team sports, cycling, aerobics and going to the gym are associated with the biggest reductions, according to the largest observational study of its kind.
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However, more exercise was not always better, and the study found that exercising for 45 minutes three to five times a week was associated with the biggest benefits.
The study, published in journal The Lancet Psychiatry, included all types of physical activity – from childcare, housework, lawn-mowing and fishing to cycling, going to the gym, running and skiing.
The study authors used data from 1.2 million adults across all 50 US states who completed a questionnaire called the Behavioural Risk Factor Surveillance System survey in 2011, 2013, and 2015.
It included demographic data, as well as information about physical health, mental health, and lifestyle behaviours.
Participants were asked to estimate how many days in the past 30 days they would rate their mental health as “not good” based on stress, depression and emotional problems.
“The specifics of the regime, like the type, duration, and frequency, played an important role in this association”
They were also asked how often they took part in exercise in the past 30 days outside of their regular job, as well as how many times a week or month they did this exercise and for how long.
All results were adjusted for age, race, gender, marital status, income, education level, employment status, body mass index, self-reported physical health and previous diagnosis of depression.
On average, participants experienced 3.4 days of poor mental health each month.
Compared to people who reported doing no exercise, people who exercised reported 1.5 fewer days of poor mental health each month – a reduction of 43.2%.
The reduction in number of poor mental health days was larger for people who had previously been diagnosed with depression, where exercise was associated with 3.75 fewer days of poor mental health compared with people who did not exercise – equivalent to a 34.5% reduction.
Overall, there were 75 types of exercise recorded and these were grouped into eight categories – aerobic and gym exercise, cycling, household, team sports, recreational activity, running and jogging, walking, and winter or water sports.
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All types of exercise were associated with improved mental health. However, the strongest effects were seen for team sports, cycling, aerobic and gym exercise.
Even completing household chores was associated with an improvement of around half a day less of poor mental health each month, noted the researchers.
The highlighted that how often and for how long people completed exercise was also an important factor.
Those who exercised between three and five times a week had better mental health than people who exercised less or more each week.
For example, exercising three and five times a week was associated with around 2.3 fewer days of poor mental health compared with people who exercised twice a month.
Exercising for 30-60 minutes was associated with the biggest reduction in poor mental health days – around 2.1 fewer days of poor mental health compared with people who did not exercise.
Small reductions were still seen for exercising more than 90 minutes a day. But doing so for more than three hours a day was associated with worse mental health than not exercising at all.
The study authors noted that people doing extreme amounts of exercise might have obsessive characteristics which could place them at greater risk of poor mental health.
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Study author Dr Adam Chekroud, from Yale University, said: “Exercise is associated with a lower mental health burden across people no matter their age, race, gender, household income and education level.
“Excitingly, the specifics of the regime, like the type, duration, and frequency, played an important role in this association,” he said, highlighting the idea of matching a specific exercise regime to help people improve mental health.
He noted that, previously, researchers had believed that the more exercise people did, the better for their mental health, but he highlighted that the new study suggested that this was not the case.
“Doing exercise more than 23 times a month, or exercising for longer than 90 minute sessions is associated with worse mental health,” said Dr Chekroud.
He added: “Our finding that team sports are associated with the lowest mental health burden may indicate that social activities promote resilience and reduce depression by reducing social withdrawal and isolation, giving social sports an edge over other kinds.”
“There is gathering interest and momentum around research into exercise as a treatment for mental health disorders”
Writing in a linked comment in the same journal, Dr Gary Cooney, from the Gartnavel Royal Hospital, said: “There is gathering interest and momentum around research into exercise as a treatment for mental health disorders.”
He said: Patients, particularly those reluctant to pursue medication or psychological approaches, are drawn to the self efficacy of exercise, the ability to attain a degree of agency in their own process of recovery.
“Mental health professionals, for their part, recognise the urgent need to address the comparatively poor physical health outcomes in the psychiatric patient population,” said Dr Cooney.
He added: “With very high rates of physical comorbidity, and marked reductions in life expectancy, an intervention that might improve both mental and physical health is of particular clinical interest.”