Laughter appears to cause the endothelium to dilate or expand in order to increase blood flow, according to a study conducted at the University of Maryland School of Medicine in Baltimore.
When the same group of study volunteers was shown a movie that produced mental stress, their blood vessel lining developed a potentially unhealthy response called vasoconstriction, reducing blood flow. That finding confirms previous studies, which suggested there was a link between mental stress and the narrowing of blood vessels.
"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 principal investigator Michael Miller, M.D., director of preventive cardiology at the University of Maryland Medical Center.
The study included a group of 20 healthy volunteers. Each volunteer was shown part of two movies at the extreme ends of the emotional spectrum. They were randomised to first watch either a movie that would cause mental stress or a segment of a movie that would cause laughter. A minimum of 48 hours later, they were shown a movie intended to produce the opposite emotional extreme.
There were no differences in the baseline measurements of blood vessel dilation in either the mental stress or laughter phases. But there were striking contrasts after the movies were seen. Brachial artery flow was reduced in 14 of the 20 volunteers following the movie clips that caused mental stress.
In contrast, beneficial blood vessel relaxation or vasodilation was increased in 19 of the 20 volunteers after they watched the movie segments that generated laughter. Overall, average blood flow increased 22 percent during laughter, and decreased 35 percent during mental stress.
MEDICA.de; Source: University of Maryland Medical Center