Näslund has some clear advice when it comes to humor. "Build up your own humor library," she says. "If you spot a gag, a funny picture or a cartoon that makes you laugh hysterically, share it. It is absolutely forbidden to keep a good joke to your self. Humor must be shared with others."

She wrote her first book on the subject in 1990 and published a second version of the book containing the latest research results nine years later. She has continuously followed research into humor and its effect on health.

"Humor's positive effect on our health is old knowledge, it's even mentioned in the Bible," she says. "During the Middle Ages doctors were aware of its healing effects, but it eventually sank into oblivion. Instead, doctors became more interested in medical treatment and machines."

One person who inspired Näslund is Norman Cousins, a writer, editor, citizen diplomat, promoter of holistic healing and unflagging optimist. During one of his journeys he developed the crippling and life-threatening collagen disease. His own theory was that stress and negative experiences had caused the illness. If that was the case, he thought, why shouldn't positive things and humor help him to recover.

So he started to treat himself with daily doses of belly laughter, all in consultation and partnership with his sometimes skeptical physicians. Through his experience of treating himself, he wrote the book Anatomy of an Illness as Perceived by the Patient: Reflections on Healing and Regeneration.

"Humor has become part of medical treatment again," says Näslund. "In many hospitals there are humor rooms where patients can read funny literature or watch funny movies. At Astrid Lindgren's hospital for children in Stockholm, for example, clowns visit sick children, helping them to cope with their stay in hospital."

Näslund also believes that people in general are more aware of the positive effects of humor. But it can be hard to measure the effects scientifically. When does the effect becomes obvious; in a month, a year?

"Common sense says that someone who finds something joyful, even in the most stressful situation, gets less stressed," she says. "I think that we all can agree on that.

"Research shows that a good belly laughter has an effect on the immune system and that humor can ease pain. There is a test called the cold pressure test where people  puts their hands in a bucket of ice water, which gets quite painful after a short while Their pain tolerance was measured before, immediately after, and twenty minutes after watching a funny movie. Through the tests, scientists have determined that humor actually eases pain and the effect lasts for at least 20 minutes."

On the other hand, she says, it can be hard to distinguish if the actual laughter is giving a relaxing effect or if feeling joyful inside is enough. What does it take to produce a positive effect? Are people who own dogs or collect rare antics happier then other people? Does it give them a relaxing, joyful feeling? Maybe it is enough to feel the nice fur from a dog to make you happy and less stressed.

When measuring the effects of humor it is, of course, important to look at someone's whole life, Näslund says. If a person has a very positive and humorous personality on one hand, but tends to eat, smoke and drink too much on the other hand, the positive effects will fail to materialize.

"I think the information society has made it easier and faster to share humor with each other," Näslund says. "The appreciation and awareness of comedy has definitely increased. Look at all the stand-up and other comedies on TV, for example. Not to mention the internet, which is loaded with humor sites and comedy. And I believe that most people enjoy having a gag being sent to them by e-mail or SMS, for example. A minute's laugh – that’s like vacation for the body of a stressed office worker."

Näslund is convinced that, in the future, researchers will develop more advanced methods of measuring humor and its effect on our health and gain a better understanding of the differences in what people think is funny. This will make research methods more accurate.  She also believes that it will be more common for people to use humor as method of finding well being; for example, team exercises in laughter.

"My own awareness has definitely increased," she says. "Since I started to write about humor I have become far more aware of its benefits. But all kinds of humor are not beneficial. Aggressive, negative, or discriminating humor or humor based on disabilities doesn't have positive effects on anyone.

"I would encourage people to start training their funny side. Everyone can do that. If you learn how to use humor for a more positive, healthy way of living you will be able to get more support both at work and at home. More people will be interested in being with you and you will find it easier to be creative at work, be more appreciated and probably receive a much higher salary."