A new large-scale United States study has found that people who exercise report having 1.5 fewer days of poor mental health a month, compared to people who do not exercise. However, working out too much could actually have the opposite effect.

Carried out by a team at Yale University, Massachusetts General Hospital and the Laureate Institute for Brain Research, U.S., along with the University of Oxford, United Kingdom, this is the largest observational study of its kind. It looked at more than 1.2 million people in the U.S. to investigate the influence of exercise type, frequency, duration and intensity on mental health.

Participants were asked to complete surveys in 2011, 2013 and 2015, answering questions on their physical health, exercise behaviors and their mental health, reporting on how many days they would rate it as “not good” based on stress, depression and emotional problems.

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The study did not take mental health disorders other than depression into account.

The researchers included 75 kinds of exercise in the study, from childcare, housework, lawn-mowing and fishing to cycling, running and skiing. They also took into account factors like age, gender and previous diagnoses of depression.

On average, participants experienced 3.4 days of poor mental health a month. However, those who exercised reported two days of poor mental health each month, 1.5 fewer days than those who reported doing no exercise, and a reduction of 43.2 percent.

“Exercise is associated with a lower mental health burden across people no matter their age, race, gender, household income and education level,” said study co-author Dr. Adam Chekroud. “Excitingly, the specifics of the regime, like the type, duration and frequency, played an important role in this association.”

All the types of exercise included in the study were associated with improved mental health. Even doing household chores was linked to a 10 percent reduction in poor mental health days a month, equal to around half a day. The largest reductions were seen for team sports (22.3 percent reduction), cycling (21.6 percent), and aerobic and gym activities (20.1 percent).

“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,” explained Dr. Chekroud.

However, when it came to how often and how long people should exercise for to reap the benefits, it appeared that more was not always better.

Those who exercised for 45 minutes, three to five times a week, had better mental health than those who exercised less or more each week. Dr. Chekroud said, “Previously, people have believed that the more exercise you do, the better your mental health, but our study suggests that this is 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.”

The results were published in The Lancet Psychiatry. JB

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