Laughing until it hurts is unquestionably a great thing. Countless studies have highlighted its wondrous health benefits, which include bolstering the immune system, increasing blood flow and oxygen intake, and helping control blood sugar levels. One oddball study even seemed to demonstrate that laughter can help increase a woman's fertility: Would-be moms undergoing in-vitro fertilization who were entertained by clowns (hey, whatever works) had a 36 percent chance of becoming pregnant versus a 20 percent control group.

Laughter truly is the best medicine. But it turns out you can have too much of a good thing.

A new study published in the British Medical Journal highlights some of the rare occurrences in which laughing too hard has actually proven dangerous to a patient's health. The research, conducted by the University of Birmingham's R. E. Ferner and Oxford University's J. K. Aronson, amassed several decades' worth of scientific literature.

In addition to reaffirming laughter's intrinsic physiological benefits and pointing out some underlying conditions that can give you a mysterious fit of the giggles (epilepsy, for example), researchers underscored some of laughing's hidden dangers.

Elizabeth Preston at Inkfish explains:

Laughter, according to various researchers, can lead to syncope (fainting), arrhythmia, and cardiac rupture. In asthmatics, laughing can trigger an attack. Laughing can even cause pneumothorax, a collapsed lung. People with cataplexy, a rare condition tied to narcolepsy, may suddenly lose all their muscle strength and collapse during a fit of laughter. An especially good laugh can make a person's hernia protrude, or dislocate someone's jaw. [Inkfish]

There are other disturbing ways laughter can kill us. As James Hamblin, MD, pointed out in an essay for Splitsider in 2011, "If you happen to be walking around with an aneurysm in your brain (one to six percent of us, most unknowingly), a single laugh could cause that aneurysm to rupture."

It's particularly dangerous if you have a bad heart, too:

Similarly, if you have bad coronary artery disease (like millions of Americans), anything that gets your heart rate up can potentially cause some atherosclerotic plaque in your coronary arteries to rupture, dislodge, and block the arterial blood flow. That’s a heart attack, which can of course kill you. This would happen to the same people you read about who never exercise and suddenly decide to shovel snow (1,200 American deaths annually) or have sex, but die instead. [Splitsider]

It's all fun and games until someone ruptures a blood vessel.

That said, a life without laughter probably isn't worth living anyway. So try not to think about it too hard the next time you're re-watching old episodes of Chappelle's Show or something.