Background: The beneficial effect of humour on health has long been recognised anecdotally and intuitively but studying and quantifying that effect is difficult. 'Studying humour is like dissecting a frog--you may know a lot but you end up with a dead frog.' (Mark Twain)
Objective: To describe some of the psychological and physiological effects of laughter and the health benefits of humour.
Discussion: Stress reduction has been shown to improve outcomes in the treatment of many health problems. While there are inherent difficulties in structuring studies to assess the impact of humour and laughter on health, positive psychological and physiological responses to laughter have been demonstrated in a variety of settings. In particular, laughter has a role in stress hormone reduction, improving mood, enhancing creativity, pain reduction, improving immunity and reducing blood pressure.