Since 2000, Wilson said, he has trained more than 1,500 laughter leaders who have created about 200 laughter clubs, a large number of them associated with hospitals, nursing homes and churches.
At the Angela Hospice and other care centers in Michigan, laughter leader Mike Millington works with patients who suffer from Alzheimer's disease, cancer and other illnesses.
"You obviously have to adapt laughter therapy to the group you are dealing with," he said. "But laughter is so primal, that you can really have breakthroughs. I've seen people who are confined to wheelchairs and dragging around IV poles laugh so hard their mood improves, and they get a pretty good workout."
Laughter leaders don't need to be stand-up comics, but a sense of humor about your vocation doesn't hurt. That still doesn't mean the therapy can't be useful for people in the most serious of situations.
At the Pentagon, U.S. Army Reserve Col. James Scott says his laughter programs give family members of those serving in the National Guard a guilt-free opportunity to relax and have a little fun, especially when a loved one is deployed overseas and facing a dangerous assignment.
"Laughter is an important stress-management tool," he said. "When you laugh, the brain stops thinking. It's a proven way to keep your mental balance."
Scott says he begins his programs in uniform, explaining the benefits of laughter with a PowerPoint slide show. Then he leaves briefly, changes into shorts and a T-shirt, reintroduces himself as "Col. Laughter" and invites everyone to "get silly." Many choose to watch, rather than participate, and then later join in.
In the last two years, the colonel has suffered only one "laughter casualty" -- and that phrase is not military jargon that he's cooked up to adapt his workshop to Army life.
A laughter casualty is anyone in a laughter workshop who leaves with a bad case of uncontrollable giggles. Perhaps it's the only sort of casualty the Army -- or Wilson's World Laughter Tour -- doesn't regret having to report.
Scott's classes have gone well enough for him to train 15 to 18 Army Reserve officers to bring workshops on a more regular basis to military families in Kansas, Texas, Idaho and Indiana.
The medical world started taking note of the possibilities of therapeutic laughter after Norman Cousins book, "Anatomy of an Illness," came out in 1979. In it, he describes how watching Marx Brothers movies, "Candid Camera" and other comedies helped him fight ankylosing spondylitis, a life-threatening disease of the joints and connective tissue, that left him in excruciating pain with few options for treatment.
One of the things Cousins documented was that a 10-minute belly laugh could give him two hours of painless sleep. "What you begin to appreciate is the profound effect that positive emotions can have on the physical body," said Alex Zautra, professor of psychology at Arizona State University.
Zautra recently conducted a long-term study of 124 women with osteoarthritis and related illnesses. While many would assume that patients in good spirits would be better able to deal with pain, Zautra's research, published in the April issue of The Journal of Consulting and Clinical Psychology, suggests the ability to manage and conquer pain can largely be predicted by a patient's frame of mind.