epetitive laughter could have the same effects on the body as exercise, according to a new study.
Results of the study, from Loma Linda University's Schools of Allied Health (SAHP) and Medicine, showed that laughing not only enhances a positive mood, but lowers stress hormones, increases immune activity, and lowers cholesterol and blood pressure, similar to moderate exercise.
In the study, 14 healthy volunteers were recruited to a three-week study to examine the effects that eustress (mirthful laughter) and distress have on modulating the key hormones that control appetite.
During the study, each subject was required to watch one 20-minute video at random that was either upsetting (distress) or humorous (eustress) in nature.
During the study, the researchers measured each subject's blood pressure
and took blood samples immediately before and after watching the respective videos.
Each blood sample was separated out into its components and the liquid serum was examined for the levels of two hormones involved in appetite, leptin and ghrelin, for each time point used in the study.
When the researchers compared the hormone levels pre- and post-viewing, they found that the volunteers who watched the distressing video showed no statistically significant change in their appetite hormone levels during the 20-minutes they spent watching the video.
In contrast, the subjects who watched the humorous video had changes in blood pressure and also changes in the leptin and ghrelin levels.
Specifically, the level of leptin decreased as the level of ghrelin increased, much like the acute effect of moderate physical exercise that is often associated with increased appetite.
Dr. Lee S. Berk, a preventive care specialist and psychoneuroimmunology researcher at Loma Linda University's Schools of Allied Health (SAHP) and Medicine, said that this research does not conclude that humour increases appetite.
"The ultimate reality of this research is that laughter causes a wide variety of modulation and that the body's response to repetitive laughter is similar to the effect of repetitive exercise," he said.
"The value of the research is that it may provide for those who are health care providers with new insights and understandings, and thus further potential options for patients who cannot use physical activity to normalize or enhance their appetite," he added.
The study is being presented at the 2010 Experimental Biology conference.