Not So Funny: The Strange Risks of Laughter
Credit: Embarrassed woman via Shutterstock

Laughing appears to bring health benefits, but not always — for some, a fit of giggles can have serious consequences, according to a new study that reviewed the effects of laughter.

The researchers reviewed studies on laughter published between 1946 and 2013. They found much evidence that laughing really is good for you. For example, laughing has been shown to improve blood-vessel function and reduce stiffness of the arteries, which is a risk factor for heart problems such as heart attacks. One study found that people who laugh easily have a reduced risk of coronary heart disease. [15 Weird Things Humans Do Every Day, and Why]

Laughing may also be good for your waistline. A 2006 study suggested that 10 to 15 minutes of genuine laughter a day may burn up to 40 calories.

Another study, published in 2011, found that laughing increases a person's tolerance to pain, which the authors suggest is due to the release of endorphins.

But in rare cases, laughing can be risky, the review found.

One woman with a condition that causes a hole in the heart experienced a stroke after laughing uproariously for three minutes, the researcher said.

And some people have accidentally breathed in foreign objects while trying to catch their breath during laughter. Laughing can even dislocate the jaw, studies show. And just like a cough or a sneeze, laughter has the potential to spread infectious diseases, the researchers said.

"Laughter is no joke," the researchers wrote today (Dec. 12) in a special Christmas issue of the British Medical Journal (BMJ) — a lighthearted edition of the journal that includes real research.

While laughter carries a low risk of harm, "our review refutes the proposition that laughter can only be beneficial," said the researchers, from City Hospital Birmingham in the United Kingdom.

Still, it remains to be seen whether "sick jokes make you ill, dry wit causes dehydration or jokes in bad taste [cause] dysgeusia (distortion of sense of taste)," the researchers joked.

Follow Rachael Rettner @RachaelRettner. Follow LiveScience @livescience, Facebook & Google+. Original article on LiveScience.