Laughter works on our physiological systems

The first hint was given by Norman Cousins, political journalist and one time Adjunct Professor of Medical Humanities for the School of Medicine at the University of California, Los Angeles, in the account of his recovery from Marie-Strumpell's disease (ankylosing spondylitis), (although this diagnosis is currently in doubt and it has been suggested that Cousins may actually have had reactive arthritis). [Reference: Wikipedia] "In Anatomy of an illness" Cousins wrote: "I made the joyous discovery that ten minutes of genuine belly laughter had an anesthetic effect and would give me at least two hours of pain-free sleep". "When the pain-killing effect of the laughter wore off, we would switch on the motion picture projector again (to watch Marx Brothers films) and not infrequently, it would lead to another pain-free interval." [Reference: Wikipedia]

In the late 1960's Dr William Fry (psychiatrist working at Stanford University, California) began to examine the physiological effects of laughter. He showed that laughter causes the body to produce endorphins which are our body's natural pain killers. [Reference: Certified Laughter Yoga Leader training manual of Dr Madan Kataria.]

I have heard an anecdotal story of a doctor living in Brazil who successfully tested the pain killing effect of laughter when she badly injured her leg is a car accident and underwent two operations without artificial anesthetic using only laughter to kill the pain.