We all know it’s good for us to laugh. But maybe you didn’t know just HOW good it is!

"The art of medicine consists of keeping the patient amused while nature heals the disease.” So said the atheist Voltaire. Well, he got one thing right anyway. Many others have purported the benefits of laughter. “When we laugh, natural killer cells which destroy tumours and viruses increase, along with . . . T-cells (important for our immune system) and B-cells (which make disease-fighting antibodies). As well as lowering blood pressure, laughter increases oxygen in the blood, which also encourages healing.” ("Science of Laughter” Discovery Health Website) “Without humor one’s thought processes are likely to become stuck and narrowly focused leading to increased distress.” (Association for Applied and Therapeutic Humor) “Laughter is very powerful medicine. It can lower stress, dissolve anger and unite families in their resolve to overcome troubled times.” (University of Nebraska)
I take it we adults don’t laugh as much as they should. “By the time a child reaches nursery school, he or she will laugh about 300 times a day. Adults laugh an average of 17 times a day.” (“Science of Laughter” Discovery Health). Science has found that laughter improves brain function, causes deeper breathing, decreases stress hormones, increases infection fighting antibodies, and increases attentiveness, heart rate, and pulse. “Laughter can be a great workout for your diaphragm, abdominal, respiratory, facial, leg, and back muscles. It massages abdominal organs, tones intestinal functioning, and strengthens the muscles that hold the abdominal organs in place. Not only does laughter give your midsection a workout, it can benefit digestion and absorption functioning as well. It is estimated that hearty laughter can burn calories equivalent to several minutes on the rowing machine or the exercise bike.”
So laughter is good medicine. But this is nothing new. Three thousand years ago Solomon wrote, “A merry heart doeth good like a medicine: but a broken spirit drieth the bones.” (Proverbs 17:22) Paul said we are to “Rejoice in the Lord always.” So have a good laugh today. It’s healthy, for God designed us to enjoy life.

http://www.helpguide.org/life/humor_laughter_health.htm