Many studies suggest that exercising can help people deal with mental health issues and boost well-being. A new observational study — the largest of its kind to date — confirms this, but it also extends a caution: too much exercise may negatively affect mental health.

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New research finds that you can get too much exercise and explains how much physical activity will actually benefit your mental health.

Recently, researchers from Yale University in New Haven, CT, have analyzed the data of 1.2 million people all across the United States to gain a better understanding of how exercise affects a person’s mental health, and which types of excercise are best for a mood boost.

More importantly, they also asked how much exercise is too much.

The researchers found that different kinds of team-oriented sports, cycling, and aerobic exercise are the most beneficial to mental health. They report this finding, and others, in a paper now published in The Lancet Psychiatry.

“Depression is the leading cause of disability worldwide, and there is an urgent need to find ways to improve mental health through population health campaigns,” notes study author Dr. Adam Chekroud.

“Exercise,” he adds, “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. We are now using this to try and personalize exercise recommendations, and match people with a specific exercise regime that helps improve their mental health.”

Dr. Adam Chekroud

The study participants were recruited from across the U.S. and had all participated the Behavioural Risk Factor Surveillance System survey in 2011, 2013, and 2015.

For their analysis, the researchers used not only demographic information, but also data about the participants’ mental and physical health, as well as their health-related behaviors. The only specific mental health disorder that the researchers took into account, however, was depression.

As for the types of exercise included in the study, the researchers looked at many different kinds of activities, including performing childcare, doing housework, cycling, going to the gym, and running.

The volunteers provided estimates of how often they had faced poor mental health during the past 30 days. They also reported how often they had exercised over the same period, and for how long.

Dr. Chekroud and team adjusted the results of their analysis for any potentially impacting factors, including the study participants’ age, race, and biological sex, as well as their marital status, income, education level, and body mass index (BMI).

On average, the participants reported experiencing 3.4 days of poor mental health per month. However, compared with people who did not engage in any type of exercise, those who did exercise had 1.5 fewer days of poor mental health per month.

Moreover, the difference was even more obvious when it came to people with a previous diagnosis of depression, as those who exercised had 3.75 fewer bad days per month than their non-exercising peers.

Any and all types of exercise seemed to help manage mental health issues. However, the ones that appeared to be more useful were team sports, cycling, aerobic exercise, and gym-based exercise.

Nevertheless, even activities that may not usually be thought of as “exercise,” such as doing chores around the house, were linked with better mental health.

The scientists also found that the association between better mental health and exercise — which amounts to a 43.2 percent reduction in instances of poor mental health — was greater than the association between it and other modifiable factors.

People with a college education experienced a 17.8 percent reduction in bad mental health days compared with those with no college education; those with a healthy-range BMI experienced a 4 percent reduction compared with people with obesity; and people with higher earnings saw a 17 percent reduction of poor mental health days compared with participants with low-salary ranges.

Dr. Chekroud and colleages found that an important factor for mental health was how often people exercise, and for how long. Also, the researchers noted, there really is such a thing as too much exercise.

Of the cohort whose data they analyzed, the team saw that those who exercised two to three times per week tended to have better mental health than both those exercised more infrequently and than those who exercised more often.

The researchers found that the participants who benefited most in terms of mental health were those who exercised for 30–60 minutes three to five times per week.

People who were physically active for over 90 minutes every day also saw some improvement in their mental health. However, participants who exercised for over 3 hours actually had worse mental health than those who did not exercise at all.

“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,” says Dr. Chekroud.

However, “Doing exercise more than 23 times a month, or exercising for longer than 90 minute sessions is associated with worse mental health,” he adds.

This, the researchers believe, may be because people who exercise for many hours at a time and who do so frequently may be exhibiting obsessive behaviors associated with poor psychological and emotional outcomes.