Previous psychoneuroimmunology research has shown evidence that laughter improves immunity. The present study was done to see how laughter changes stress and natural killer cell (NK) levels. Low NK levels are associated with increased morbidity in cancer and HIV disease.

Laughter may reduce production of cortisol and increase the production of beta-endorphins to improve immunity. Cortisol has been shown to reduce NK levels.

Thirty-three women were tested since most previous studies were done on males. The subjects were shown a humorous video and a control group was shown a travel video. Self-reported stress and arousal levels, mirthful laughter, and NK levels were measured.

Both the subjects and the controls experienced some stress relief by watching a video. The subjects who experienced mirthful laughter had the greatest reduction in stress.

The subjects who watched a humorous video and responded with outright laughter had great increases in NK cell levels. Those who watched the humorous video and had little reaction had a reduction in their NK cell levels. In general, the subjects with the greatest amount of stress had the least improvement in NK cell activity.

CONCLUSION: Self-reported stress was reduced in the group that observed the humorous video and the group which watched the travelogue. The subjects with the best scores of observable laughter in response to the video showed the most increase in immune levels. Observable laughter seems to cause the greatest stress relief and the greatest increases in NK cell levels. The present study was only done on women.

NOTE: Dr. Norman Cousins wrote “Anatomy of an Illness.” This book was important at the start of the use of humor therapeutically in disease. Dr. Cousins developed a neurological disease that had no effective treatment at the time. He checked himself into a hotel, took large doses of I.V. vitamin C and watched hours each day of humorous videos. This seemed to cure his illness and the book it the story of his experience.

Psychoneuroimmunology studies the relationships between the mind, the nervous system and the immune system. Cortisol is produced by the adrenal glands when the person is under stress. The present study is an example of how behavior can alter immunity and NK cell activity.

Read ahout how happiness is contagious.

To read the author’s abstract of the article click on the link to the author’s title of the article above.

PMID: 12652882.

Summary #165.