Laughter stimulates the immune system.

Dr Lee Berk, of Loma Linda University School of Medicine, demonstrated that laughter:

  • lowers serum cortisol levels
  • increases the number of T-cells that have helper/suppressor receptors; and
  • increases the number and activity of natural killer cells that fight abnormal cells such as cancer.

Other research supports these findings. In Laughter & The Immune System: a serious approach, Dr Lee Berk and Dr Stanley Tan published a study conducted by Barry Bittman, neurologist and pioneer in psychoneuroimmunology (how emotions affect the immune system).

Blood of patients was analysed before, during and after watching a humorous video. The test found a 'significant' boost to immune function, including higher levels of anti-bodies and natural killer cells which are the body's defence against aberrant cells such as cancer.

The positive effects of laughter on the immune system continued the next day; in addition, levels of Plasma Immunoglobulin, Plasma Cytokine Gamma Interferon and killer cells remained high 12 hours later.

Norman Cousins found humour and laughter relieved the pain of his ankylosing spondylitis (a painful, degenerative form of arthritis primarily affecting the spine). In 1969 he collaborated with his physician Dr Hitzig. He watched funny films and read humorous books, and found that only 10 minutes of laughter gave him two hours of pain-free sleep. There was physiological evidence in his lower sedimentation rate (a measure of inflammation). The reduction not only held, but was cumulative. He popularised the benefits of laughter in his books Anatomy of an illness as perceived by the patient: reflections on healing (1979) and Head first: the biology of hope and the healing power of the human spirit (1989).

His theory that positive emotions had a positive effect on health lead to modern research.  Based at UCLA Medical School, he established the Humour Research Task Force to co-ordinate and support world-wide clinical research on humour.

Other studies also showed that laughter helped reduce pain, although much of this is anecdotal. In 1928 Dr James Walsh noted in his book Laughter and Health that laughter reduced the pain after surgery and promoted wound healing.

Ljungdahl reported that women with painful muscle disorders got significant pain relief after a course of humour therapy. (L. Ljungdahl, Journal of the American Medical Association 1989).

Young girls with burns were shown cartoons during very painful hydrotherapy. Their perception of pain was reduced. The study was done by ML Kelly and published in the Journal of Applied Behaviour Analysis (1984).

Prolonged stress creates unhealthy physiological changes. Stress causes the adrenal glands to release cortico steroids and high levels have an immunosuppressive effect. Laughter is an antidote. Berk, Tan, Fry et al reported this in Neuroendrocrine and stress hormone changes during mirthful laughter, American Journal of the Medical Sciences. 298(6), 390-396.

Laughter, like exercise, reduces the heart rate.

William Fry in 1971 first demonstrated that laughter increases the heart rate, blood pressure, oxygen consumption, and works the muscles in the face and stomach. Shortly after, these levels drop, providing a relaxation response.

Dr David Garlick of the University of NSW School of Physiology and Pharmacology studied the effects of laughter on the respiratory system. Abdominal movements were measured during funny videos and documentaries. Laughter was followed by a long sigh and a large intake of breath, leading to better respiratory movement.

For details of the research mentioned above and further references click here.