The Pilgaard-Dahl syndrome: laughter-induced pneumothorax - one of the many potentially detrimental consequences of laughter.

In this article we propose the eponym Pilgaard-Dahl syndrome (named after two Danish revue actors). The syndrome consists of laughter-induced pneumothorax in smoking middle-aged men when exposed to hearty humour. The epidemiology and pathophysiology of spontaneous pneumothorax - in particular the Pilgaard-Dahl syndrome - is described. Finally, the occurrence of other detrimental effects of laughter as syncope, extreme bradycardia, asthma bouts, headache, stroke, death, and incontinence are described, as well as initiatives expected to minimise the occurrence of good mood are proposed.