In that group, people who exercised had seven days of poor mental health a month compared to 11 days for those who didn't exercise.
Engaging in exercises such as cycling, aerobics and gymming for more than three hours a day can worsen mental health than not exercising at all, a study has found.
Exercise improves mental health: what is the maximum limit?
Dr Dean Burnett, neuroscientist and honorary research associate, from the school of psychology at Cardiff University, said the link between exercise and mental health had been hard to pin down but this large study "strongly suggests that there is a definite association between the two". "We are now using this to try and personalise exercise recommendations, and match people with a specific exercise regime that helps improve their mental health".
However the research also found that more exercise was not always better for mental health and well-being, with people who exercise every day reporting lower moods.
The investigation was focused on 1.2 million adults across the United States who had participated in the Behavioral Risk Factor Surveillance System survey in 2011, 2013, and 2015.
Even completing household chores was associated with reduction in poor mental health days of around 10 per cent, or around half a day less each month, the researchers said.
Exercise reduces the risk of cardiovascular disease, stroke, diabetes, and mortality from all causes, but its association with mental health remains unclear.
After adjusting for factors such as income, marital status, race, age, BMI, previous diagnosis of depression, education level, and employment status the average number of days reported as being of poor mental health was 3.4 in 30 days, with participants who exercised reporting 3.4 fewer days of poor mental health; and the largest decrease in numbers of poor mental health days was seen among participants with previous depression diagnosis. The individuals reported on their physical health, mental health, and exercise behaviors.
He said the positive impact of team sports suggested that social sports activities could reduce isolation and be good for resilience, while also reducing depression.
Exercising for 30-60 minutes was associated with the biggest reduction in poor mental health days.