The ability of blood vessels to expand is known as vasodilation. Poor vasodilation means that passageways may be blocked and blood flow may be cut off. The result is an increased risk of heart attacks and strokes.
In the study, 20 healthy men and women watched clips of two movies--a violent battle scene from "Saving Private Ryan" or a humorous scene from a comedy such as "Kingpin." Each participant's vasodilation was measured prior to the movie and again afterward.
The results were "dramatic." Of the 20 participants who saw the stressful film, 14 had significantly reduced blood flow. However, after watching the funny film, 19 of the 20 volunteers had significantly increased blood flow. Specifically:
- Blood flow decreased by about 35 percent after experiencing stress
- Blood flow increased by 22 percent after laughing, which is equivalent to what happens after a 15- to 30-minute workout
Past studies have found that stress hormones like adrenalin and cortisol, which is released when a person is stressed, may harm the body by suppressing the immune system and constricting blood vessels. On the other hand, the researchers believe laughing causes the body to release beneficial chemicals called endorphins, which may counteract the effects of stress hormones and cause blood vessels to dilate.
In a similar manner, laughing may also boost the immune system and reduce inflammation, which is thought to increase the risk of various health problems.
The researchers say they have a long way to go before their hypothesis will be proven, but they point out that there's no downside to laughing and they have no problem recommending it to their patients.