A merry heart does good, like medicine, but a broken spirit dries the bones." These words, recorded in the biblical book of Proverbs (17:22) almost 3,000 years ago, have now been confirmed by medical science as a result of two recent studies reported by the Reuters news service.

In one study, Dr. Michael Miller and colleagues at the University of Maryland School of Medicine in Baltimore tested the function of blood vessels of 20 healthy volunteers as they were shown two movies—one humorous, the other stressful. They focused particularly on the endothelium, the lining of the blood vessels, where atherosclerosis (hardening of the arteries) begins.

They found that blood flow diminished in 14 of the 20 subjects after they watched stressful movie clips. Their blood flow decreased an average of 35 percent during those stressful periods.

In contrast, 19 of the 20 study subjects had increased blood flow when laughing at humorous movie segments, with blood flow increasing an average of 22 percent.

"We don't recommend that you laugh and not exercise, but we do recommend that you try to laugh on a regular basis," said Dr. Miller in reporting on the study. "Thirty minutes of exercise three times a week, and 15 minutes of laughter on a daily basis is probably good for the vascular system." He explained that "laughing may be important to maintain a healthy endothelium, and reduce the risk of cardiovascular disease."

He also explained that "the magnitude of change we saw in the endothelium is similar to the benefit we might see with aerobic activity, but without the aches, pains and muscle tension associated with exercise."

In the second study, 1,005 heart failure patients were tracked and tested for depression by Dr. Wei Jiang and colleagues at North Carolina's Duke University. Dr. Jiang reported that patients with mild depression were at 44 percent greater risk of dying than those not experiencing depression, excluding other factors such as age, marital status and original cause of the patients' heart failure.

Dr. Jiang noted that patients experiencing depression tended to not take medications properly or not exercise and were more prone to making unhealthy lifestyle choices in diet and smoking.