The effect of laughter on physical and mental well-being is the purview of gelotology, the study of humor and laughter. This new field of study has found that the longer and more often you laugh, the greater the health benefits.

Various kinds of stimuli cause laughter, explained Michaela Schaeffner, head of the Munich-based Association of German Laughter Therapists. They include emotional stimuli such as a good mood while on holiday, mental stimuli such as a funny joke and physical stimuli such as tickling.

"When it comes to mental and physical stimuli, the key is an element of surprise - a sense of contrast. So for them, I always need a communicative situation," Schaeffer said.

When the brain receives an appropriate stimulus, it sets laughter in motion. "More than 100 muscles are involved, from facial muscles to respiratory muscles," noted Professor Carsten Niemitz, director of the Institute of Human Biology and Anthropology at the Free University of Berlin.

"Hearty laughter engages the entire body: The head moves, the body bends. Specialists call this 'generalisation'," Niemitz said.

Breathing during laughter is deeper than usual, which affects the whole body.

"More oxygen flows to the body's cells, the bronchia are ventilated, catabolic processes are advanced, muscles relax, the heart and circulation are stimulated," said Michael Titze, lecturer at the March Institute of Psychotherapy in the Brandenburg town of Baruth.

In addition, laughter boosts healing. A laughing person's brain blocks production of stress hormones such as adrenaline and cortisone. But that's not the only benefit. "When someone laughs, more serotonin - sometimes called 'the happiness hormone' - is secreted. So, if you laugh a lot, you'll feel better," Niemitz said.

Studies done in the United States suggest that laughter enhances the body's immune system. It seems to activate T lymphocytes, which attack cancer cells, as well as gamma-interferone, which helps eliminate tumor cells. While definitive proof of this is still lacking, Niemetz said, "The sum of everyday clinical evidence is credible, and one ought to make use of it".

Laughter's psychological benefits are also worthy of attention. "Laughing together after a victory in a sporting event, for example, is an important sign of solidarity," Titze remarked.

Source: China Daily agencies