March 7, 2005 -- "Rent two comedies and call me in the morning," may sound like an unusual prescription, but a new study shows that laughter may be good medicine for the heart.
But watching a mentally stressful movie, like a war drama, may have the opposite effect, causing the lining of the blood vessels, known as the endothelium, to narrow and restrict blood flow.
"The endothelium is the first line in the development of atherosclerosis or hardening of the arteries, so, given the results of our study, it is conceivable that laughing may be important to maintain a healthy endothelium, and reduce the risk of cardiovascular disease," says researcher Michael Miller, MD, director of preventive cardiology at the University of Maryland Medical Center, in a news release. "At the very least, laughter offsets the impact of mental stress, which is harmful to the endothelium."
Miller presented the results of his study this week at the Scientific Session of the American College of Cardiology in Orlando, Fla.
Laughter Fosters Healthy Blood Vessels
In the study, researchers had a group of 20 healthy men and women watch two movies at opposite ends of the emotional spectrum and then measured the movies' effects on their blood vessels via ultrasound.
On separate days the participants watched a 30-minute segment of Saving Private Ryan, a war drama thought to cause mental stress, and Kingpin, a comedy that would cause laughter. Blood vessel reactivity was measured before and after watching the movies.
The results showed that each movie provoked strikingly different effects on blood vessel function.
For example, blood flow was reduced in 14 of the 20 volunteers after watching the movie clips that caused mental stress. But beneficial blood vessel effects and relaxation were found in 19 of the 20 volunteers after watching the funny movie.
On average, artery diameter increased by 22% during laughter and decreased by 35% during mental stress.
"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," says Miller. "We don't recommend that you laugh and not exercise, but we do recommend that you try to laugh on a regular basis. Thirty minutes of exercise three times a week, and 15 minutes of laughter on a daily basis is probably good for the vascular system."