Sun demands no reason to shine;
Water demands no reason to flow;
A child demands no reason to smile;
Why do we need a reason to laugh?
Dr. Madan Kataria, Laughter Yoga University

Laughter Yoga Clubs began with just five people in 1995, today there are over 6000 clubs in 60 countries.

Excerpt:
Los Angeles Times
March 4, 1998
A Good Guffaw a Day . . .
"Hahahaha!"
"Ho-ho-ho-ho!"
"Aaaaaahh-hahahahaha!"

"We are a singularly humorless nation," said Khushwant Singh, a journalist and author who has written five humor books. "There are too many sacred things here. The average person takes himself too seriously. Perhaps if people are seen making fun of themselves, then other people will decide that's OK."

The laughing clubs' catalyst was Madan Kataria, a jovial Bombay physician and yoga enthusiast. Three years ago, he invited four friends to Lokhandwala Park near his home. They stood in a circle and shared a laugh. Almost immediately, he says, other people began turning up.
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What is Laughter Yoga?
Learn about the Scientifically Proven Benefits of the Laughter Yoga Health and Fitness Craze:
Laughter Yoga is a unique concept developed by Indian physician, Dr. Madan Kataria.
It is fast sweeping the world and is truly a life changing experience. It combines laughter exercises with yoga breathing which brings more oxygen to the body and brain making one feel more energetic and healthy. The concept is based on a scientific fact that the body cannot differentiate between fake and real laughter. One gets the same physiological and psychological benefits. Safe, easy and scientifically proven, Laughter Yoga is a lot of fun.
Started with just five people in 1995, today it is a global phenomenon with over 6000 clubs in 60 countries.

Laughter is clinically proven to:

1. Boost the immune system. Laughing improves the body’s natural defense mechanism by increasing the amount of immunoglobulin’s and T cell’s in the body.

2. Reduce the risk of heart disease. Laughing expands the inner walls of the arteries which increases the ability of blood to flow around the body, and, this positive effect lasts for up to 45 minutes after the laughter has stopped.

3. Decrease stress. Laughing instantly reduces the levels of stress hormones such as cortisol, epinephrine (adrenaline) and dopamine, and increases the production of serotonin and endorphins which reduce effects of stress.

4. Can assist as a mild anti-depressant. Laughter boosts the production of serotonin, a natural anti-depressant. Laughter also works as an effective distraction from things that cause anxiety and anger.

5. Reduce blood pressure. When you laugh, the blood flow increases, circulation improves and your blood pressure rises. When you stop laughing, your blood pressure drops back to its baseline. This relaxing effect helps to lower your baseline blood pressure.

6. Is a natural painkiller. There are a number of studies which validate the pain relieving effects of laughter. Studies show that watching comedy films assists both children and adults to tolerate pain more easily.

7. Massage the abdominal organs. Belly laughing effectively ‘massages’ the abdominal organs. The blood flow to these organs is increased and their functioning is improved.

8. Help keep diabetes under control. A recent study showed that people who watched a funny video after meal had lower blood sugar levels than those who watched a serious film. It could be that laughter affects the neuroendocrine system, which monitors the body´s glucose levels, or it may be the effect of energy used by the stomach muscles.

9. Make you look younger. As many as 15 facial muscles work together to help you smile and laugh. This increases the blood flow around the face, bringing the circulation into even the smallest of capillaries which, in turn, helps to make you look younger and healthier.

10. Re-energize the mind and body. Laughing forces air out of lungs, and causes us to take deep inward breaths, increasing the flow of oxygen right around the body.

11. Build resilience. The ability to laugh, or at least smile, when times get tough, is the best way to reduce stress and anxiety. While a little stress actually helps to motivate us into action and to focus on the problem, laughter helps us to focus on the solution and achieve more productive outcomes.

12. Aid with sleep. Having a good laugh prior to sleep reduces stress and anxiety, promoting deep, restful sleep. Laughter also provides a mild aerobic workout, which, not only energizes you in the short term, but also helps you to sleep better.

13. Bond us to others. Laughter causes the release of oxytocin. Often called the empathy hormone, oxytocin helps bond individuals and groups together. A little laughter is great for building great teams, be they in the community or at work.

14. Is contagious. Laughing not only lifts our spirits but also the spirit of those around us. Happy people lift the spirit of those around them. Remember, a smile or laugh shared is a smile or laugh doubled.

How Smiling Can Backfire
Scientific American: If you’re reading this at a desk, do me a favor. Grab a pen or pencil and hold the end between your teeth so it doesn’t touch your lips.

Smiling Could Help With Stress: Study
Huffington Post: If you’re feeling stressed, maybe the best thing you can do is crack a smile. New research shows that smiling — and especially genuine smiling (where your eyes and mouth muscles are engaged) 

Smiling during stress may help the heart
United Press International: People who smile even though they don’t feel like it had lower heart beat levels, U.S. researcher suggest. Psychological scientists Tara Kraft and researcher suggest. Psychological scientists Tara Kraft and Sarah Pressman of the University of Kansas conducted a series of experiments involving 169 participants from a Midwestern university.

Selected References

The Untapped Power of Smiling
By Ron Gutman 
March 22 2011
DailyGood.org
Recently I made an interesting discovery while running – a simple act that made a dramatic difference and helped carry me through the most challenging segments of long distance runs: smiling. This inspired me to embark on a journey that took me through neuroscience, anthropology, sociality and psychology to uncover the untapped powers of the smile.

Does Smiling Have Positive Health Effects?
Smiling is something that everyone does and is often associated with happiness. Yes, smiling is used to show our emotions, but it so much more than that. The University of Kansas conducted a study involving 170 college students to test whether smiling has a positive impact on our mood and health. The students were randomly assigned to three groups, all of which had the students mimic a research assistant holding chopsticks between their teeth, however each group was mimicking different actions. Of the three groups, one had the students genuinely smile while the other two partook in fake smiles all while continuing to hold the chopsticks in between their teeth. Next, the students were asked to perform stressful tasks while researchers monitored their heart rates from beginning to end. In addition, the researchers asked the students to describe their mood before and after completing the tasks. The researchers found that heart rate rose while completing the stressful tasks, however the heart rate of smilers went back down to normal faster than those who forced their smiles. In addition, when the students reported their moods to the researchers, those who were smiling had a smaller decrease in mood than those who forced their smiles. The conclusion of the study was that smiling genuinely reduces stress while performing stressful tasks as well as helps the body recover quickly after the event. >>>more