Benefits include stress reducer, improving performance, enhancing self-esteem, promoting creativity, strengthening the immune system, improving ability to negotiate and make decisions, increases breathing rate, clears mucus from lungs, increases oxygen delivered to cells, stimulates enzymes that function as natural laxatives, and improves digestion. (Hafen, Brent Q., et al. Mind/Body Health. p 541-560. MA: Simon & Schuster, 1996.
Laughter tends to expand lungs and increases blood and oxygen circulation similar to the way deep breathing or exercise does. Anger and stress do the reverse. (Greenwood-Robinson, Maggie, PhD. 20/20 Thinking. p 104. NY: Avery, Putnam Special Markets, 2003.)