Laughter has its downers

Among the alarms it sounds: The force of laughing can dislocate jaws,make hernias protrude,cause asthma attacks and headaches. It can provoke cardiac arrhythmia,fainting and emphysema. Laughter can trigger the rare but possibly grievous Pilgaard-Dahl and Boerhaave’s syndromes. And ponder,briefly,the mortifying impact of sustained laughter on the urinary tract.

The analysis,Laughter and MIRTH (Methodical Investigation of Risibility,Therapeutic and Harmful),was drawn from about 5,000 studies. It appears in BMJ,which has long featured rigorously researched but lighthearted articles in its Christmas issue. A deputy editor,Dr Tony Delamothe,said that the MIRTH study was indeed peer-reviewed — presumably by a doctor with a carefully managed sense of humour.

Last spring,the MIRTH co-authors,Dr Robin E Ferner,an honourary professor of clinical pharmacology at the University of Birmingham,and Jeffrey K Aronson,a fellow in clinical pharmacology at the Oxford,who study the benefits and harms of medicines,discussed what benefit-harm they could explore in a gambit to win a coveted berth in BMJ’s Christmas issue. According to Delamothe,BMJ receives nearly 120 submissions and accepts 30. Ferner and Aronson winnowed the papers that mentioned laughter to 785,putting them into three categories: benefits (85),harms (114) and conditions causing pathological laughter (586).

The question was timely,they argued,because BMJ had not addressed laughter in a serious fashion in over a century. In 1898,it published a case study of heart failure in a 13-year-old girl after prolonged laughter. The next year,the laughter problem was raised when an editorial writer,in response to an Italian doctor’s suggestion that telling jokes could treat bronchitis,dismissively proposed the term “gelototherapy.” (Gelos is the Greek god of laughter.)

Laughter as a therapy was slow to gain traction: In 1928,The Journal of the American Medical Association gave short shrift to Dr James J Walsh’s book,Laughter and Health.

The harms,however,have been scrutinised. A 1997 discussion of Boerhaave’s syndrome,a spontaneous perforation of the esophagus,a rare though potentially lethal event,mentioned that one unusual cause is laughter. Then there is the mysterious Pilgaard-Dahl syndrome,identified in a 2010 article as a pneumothorax in middle-aged male smokers induced by laughter. “If you’re going to make asthmatics laugh heartily,” Ferner said,“they might want to have an inhaler by their side.”

Studies in recent years have concluded that laughter “reduces arterial wall stiffness” and “improves endothelial function.” Said Ferner,“We don’t know how much laughter is safe. There’s probably a U-shaped curve: Laughter is good for you,but enormous amounts are bad,perhaps.”