A regular run through the park may improve not only heart health but also mental health, a study suggests.

In a study that followed a group of middle-aged British men for 10 years, researchers found that those who got regular vigorous exercise were less likely to develop depression or an anxiety disorder over time.

The effect was modest, and there was no evidence of a benefit from other forms of activity, including physical labor at work.

Dr. Nicola J. Wiles and her colleagues at the University of Bristol report the findings in the American Journal of Epidemiology.

Past research has found that exercise can be helpful for people with mild-to-moderate depression, but studies have come to conflicting conclusions as to whether physically active people are at lower risk of developing depression or anxiety.

To study the question, Wiles’s team used data from a 10-year follow-up of 1,158 middle-aged British men. At the beginning of the study, the men reported on their exercise habits and any on-the-job physical activity. They also completed standard screening questionnaires for depression and anxiety at three points over the study period.

In general, men who reported regular vigorous exercise - such as running or playing soccer - were about one-quarter less likely than their less active peers to develop depression or anxiety over the next 5 years.

The benefit was no longer evident at the 10-year mark, however.

The findings, according to Wiles and her colleagues, are consistent with what’s been seen in exercise studies of patients with mild depression. It’s thought that exercise may directly affect depression through actions on certain brain chemicals; it might also have indirect benefits by improving self-esteem or body image.

Though exercise did not show a strong impact on men’s mental health in this study, the findings point to one more reason to get off the couch, according to the researchers.

“The widespread encouragement to lead a physically active lifestyle in order to gain the recognized benefits for physical health may also have modest short-term benefits for mental health,” they conclude.

SOURCE: American Journal of Epidemiology, April 15, 2007.