Cambridge, UK - A review from researchers at Britain's University of Cambridge showed that those who exercise are less likely to develop depression, even if they exercise less than the recommended amount.

Experts recommend that adults engage in two-and-a-half to five hours of moderate activity per week, or one hour and 15 minutes to two-and-a-half hours of vigorous aerobic exercise per week – or some combination of the two.

Adults who took a brisk walk for what amounted to two-and-a-half hours per week were less likely to develop depression than those who didn’t exercise at all, the study found.

But even those who exercised less fared better than those who didn’t exercise at all, according to researchers.

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"In this study, relatively small doses of physical activity were associated with substantially lower risks of depression," the study said.

The researchers analyzed 15 studies with nearly 200,000 participants.

Those who did about half the recommended amount of physical activity per week had an 18% lower risk of depression compared with adults who did not exercise, the study said. Participants who exercised the recommended amount had a 25% lower risk of depression than those who did not. Exercising more than the recommended amount had little effect on depression risk, according to researchers.

Many aspects of exercise can lead to improved mental health. For example, working out can increase circulation to the brain and activate the central nervous system, leading to what many refer to as a "runners high," the study claimed. More exercise can also lead to improved physical health and a better body image, which can cause a person to be more social, researchers said.

Nearly 5% of adults in the US report regular feelings of depression, according to the Centers for Disease Control and Prevention.

Among the study participants, researchers estimated that one in every nine cases of depression might have been prevented had everyone met recommended exercise guidelines.

If you or someone you know is struggling with depression, text "HOME" to 741741 from anywhere in the US, anytime. The Crisis Text Line is answered by live, trained crisis counselors.