"It turns out that what is called the best medicine occasionally does us harm," says co-author Robin Ferner, a clinical pharmacologist at the University of Birmingham, U.K. "Most of the time it makes people happy, but every now and again it kills them."
In what he describes as the BMJ's first serious look at laughter since 1899, Robin Ferner and his colleague Jeff Aronson trawled through nearly 800 studies on laughter dating back to 1946. They synthesized them in a witty and light-hearted report on the health benefits and risks of a good hearty laugh.
"We are clinical pharmacologists who spend our days worrying about the benefits and harms of medicines," says Ferner. "We thought we might look elsewhere, and laughter—'the best medicine'—seemed a worthy candidate."
It wasn't easy. A search of the scientific databases using "laugh" as a search term turned up articles on the Caribbean sponge Prosuberites laughlini; papers written by researchers named Laughter, Laughing, Laughton, and McLaughlin; and an intriguing paper titled "Another Exciting Use for the Cantaloupe," which described practicing endoscopy on melons.
"There aren't, in truth, that many good studies of the benefits of laughter," Ferner says. "It seems to be assumed that because we feel better when we laugh, we are better."
And, it seems, by and large we are. "In the rarest of circumstances, a good laugh can be harmful, but for most of us most of the time, there are few dangers; it may make us feel better; and it could make us—well, our women—pregnant."
Chuckle Away Your Chubbiness
The demonstrable physical and therapeutic benefits of laughter found by various studies over the years include greater suppleness in arterial walls, lowered risks of myocardial infarction, and improved lung function. Laughter was also found to raise the pain threshold in patients. But another study indicated that hospital clowns had no discernable effect on the distress of children undergoing minor surgery, nor was hilarity found to have much benefit for patients with severe mental disorders.
On the lighter side—so to speak—the researchers found that laughter can be a great calorie burner and thus a fun way to lose weight. Fifteen minutes of laughing can burn 40 calories, or 2,000 calories for a whole day of merriment.
A study among diabetics found that the effects of watching a comedy show, as opposed to listening to a "monotonous lecture," slowed the increase in glucose after a meal.
Laughter had measurable benefits in women undergoing IVF treatments as well. "A clown, dressed as a chef de cuisine, entertained would-be mothers for 12-15 minutes after in vitro fertilisation and embryo transfer. His saucy jokes were a recipe for success—the pregnancy rate was 36 percent in those whom he entertained compared with 20 percent in the controls," the study says.
The Downside of Cracking Up
Like any other medicine, laughter also has side effects and dangers. Overdoses can even be fatal in rare instances. BMJ's last serious look at laughter, in 1899, came on the heels of a case where a 13-year-old girl died of heart failure after a prolonged fit of uncontrollable laughter.
Such incidents are extremely rare, says Ferner. In the course of their research, they came across a couple of modern instances of people who died laughing. One woman, who had racing heart syndrome, collapsed and died after a prolonged period of intense laughter.
Respiratory side effects of laughter include inhaling foreign objects and occasionally the triggering of an asthma attack. Laughter can cause incontinence and dislocate a jaw. It can make a hernia protrude, "aiding diagnosis in children—rapture unmasking rupture. By contrast, failure to laugh is an important sign of intra-abdominal infection in children."
Studies of the psychological side effects of laughter show that it can weaken resolve and promote brand preference. And a good hearty laugh, "like many pleasurable things, including ice cream, chocolate, and sex (separately, and perhaps together), may precipitate headaches," the authors wrote.
"These conclusions are necessarily tentative," they conclude, tongue still firmly in cheek. "It remains to be seen whether, for example, sick jokes make you ill, if dry wit causes dehydration, or jokes in bad taste cause dysgeusia [distortion of the sense of taste], and whether our views on comedians stand up to further scrutiny."
As for future research, Ferner notes the field is wide open. "We limited our search to 'laughs,' and did not explicitly seek cacchinations, cackles, chortles, chuckles, giggles, grins, guffaws, smiles, smirks, sneers, sniggers, teehees, or titters; we also ignored sources of laughter (comedy, drollery, humour, jest, jocularity, whimsy, wit, and wisecracks)."