For nearly two decades, this uniquely positioned newsletter, Harvard Mental Health Letter, has delivered information, current thinking and debate on mental health issues that concern professionals and laymen alike. In the ever-changing and complex field of mental health care, the newsletter has become a trusted source for psychiatrists, psychologists, social workers, and therapists of all kinds.

Excerpt from Harvard Mental Health Letter

A good workout makes you feel better, and regular exercise not only enhances physical health but can lift mood, reduce stress, and heighten self-esteem by improving appearance and physical strength. But how useful is exercise for people with severe depression or anxiety or chronic mental illness? Hundreds of studies now show that it can help — but there are qualifications.

Many reviews and meta-analyses show that regular physical activity is correlated with improvement in clinical depression and anxiety, mild to moderate depressive symptoms, insomnia and resilience under stress. People who become or remain physically fit or active are less likely to develop clinical depression.

For example, in a study published in 2005, researchers examined the effect of a three-month exercise program on mild to moderate depression. About 80 participants were divided into five groups. Two groups took on a rigorous “public health dose” program, one of them for three days a week and the other for five days a week. Two groups instead participated in lighter “low-dose” exercise three or five days a week. A fifth group, the controls, practiced only stretching for flexibility.

Ratings of depressive symptoms on the standard Hamilton scale fell in all five groups, but the rigorous exercise program caused the biggest drop, an average of 47 percent. That made it about as effective as antidepressant medications or cognitive behavioral therapy, standard treatments for depression. The low-dose exercisers did no better than the controls, but even patients in these three groups showed some improvement. Any physical activity may have helped.