When I was a young boy, I remember my mom telling me about Norman Cousins. He was an author who was suffering with heart disease and he treated it by watching Marx Brothers movies and other comedies continually until he laughed himself back to health. He wrote a book called Anatomy of Illness in 1979 which details his story.
I'm sure there are many who would criticize his claim that laughter can cure disease. It is, however, obvious that laughter is a positive emotion, and I believe it has a positive effect on one's body. Laughter has been credited with reducing pain, increasing one's pulse, increasing blood flow and oxygenation of blood, releasing endorphins, boosting the immune system, difusing tension, and relieving stress.
I don't claim laughter can cure any disease. If I broke my leg and was sent to the emergency room, I wouldn't be content with an orderly reading to me from a joke book, but I've been surprised to learn that humor therapy is an alternative form of treatment used for many serious diseases and ailments.
It's hard to feel sick or depressed when one is laughing. Most of us feel better when we associate with jovial people who have a sense of humor and are light hearted, as opposed to grumpy people who are too serious.
Benny Hill, Jim Carey, Brian Regan, and Jim Gaffigan may do more to contribute to our good health than we know. Laughter is good medicine.