Too much exercise could be bad for your mental health, study suggests

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on December 17, 2012 at 5:02 PM, updated December 17, 2012 at 5:05 PM

exercise.jpg Researchers at Teachers College of Columbia University recently found that extremes of exercise are associated with poorer mental health. The "happy medium" for weekly exercise was between 20 minutes to an hour of exercise a day.  

CLEVELAND, Ohio — Exercise more. Most of us have heard this advice more than once.

But you can have too much of a good thing, according to one of the largest studies to date on exercise and mental health. That study, published recently in the journal Preventive Medicine, found an optimal weekly dose of exercise between 2.5 hours and 7.5 hours.

Beyond that (and below it) participants said they had poorer mental health.

"We really didn't expect this relationship," said lead researcher Carol Ewing Garber, associate professor of biobehavioral science at Teachers College of Columbia University in New York. Garber said the team had expected a linear relationship, not the U-shaped curve they found.

"We found that if you do a little less than what we generally recommend for health benefits then you had more symptoms of depression, anxiety or poor mental health," she said. "But we were really surprised that if you did more you also had worsened symptoms."

The team used self-reported data on physical activity and mental health symptoms from 7,674 adults who responded to the 2007 U.S. Health Information National Trends Survey. HINTS is a nationally representative survey on how people find, use and understand health information run by the National Cancer Institute.

People who engaged in 2 1/2 to 7 1/2 hours of exercise a week were 1.39 times more likely to have better mental health, compared to those who exercised less or greater amounts of time, Garber said.

Dr. Donald Malone, head of behavioral health at the Cleveland Clinic, said the study's findings make sense.

"When anything becomes a bit more of an obsession and takes up an inordinate amount of time, it can have a negative impact on your mental health," he said. "Whether that's work or it's exercise, we've always said 'everything in moderation.' "

Both doctors caution against concluding that excessive exercise causes poor mental health, though.

"It may be the other way around," Garber said.

Malone agreed. It could be that people who are prone to poor mental health are more attracted to extreme levels of exercise, he said.

In the current study, Malone pointed out that it was those who exercised significantly beyond an hour a day who had poorer mental health.

"If you're spending two or three hours a day exercising, there are probably some other things you're giving up that contribute healthfully to how you're thinking and behaving and how you feel about yourself," he said.

And if exercise becomes a compulsion, it may be part of a larger mental health problem like anorexia or bulimia.

"It can definitely be a signal that something else is wrong," Malone said.

At the other extreme, it's also impossible to say from the current study if a lack of exercise caused the depressive and anxious symptoms in the people who participated. Again, it may be that those with depression have a hard time finding the motivation to exercise.

Both experts caution against using the study results as an excuse not to exercise regularly. Research has shown that moderate amounts of exercise (in the optimum range highlighted in the current study) can lift mood in those with depression, they said.

"When you're able to do something that's good for you, you feel better both physically and mentally," Malone said.

"I wouldn't want people to think they have to reduce their exercise," Garber said. "Exercise is good for you, and you can actually do quite a lot of exercise and it's not associated with any adverse effects."

The researchers also looked at the association between mental health and other variables, such as age, marital status, education level, income, physical health, race and ethnicity.

Older age, college education, income over $50,000 a year and better physical health were associated with improved mental health.

Garber plans to follow up the research by asking similar questions to a large group of adolescents, and eventually develop a randomized clinical trial to better define the relationship between exercise and mental health.