Laughter is good for your psychological well-being and cardiovascular health, but (don't laugh) it could also kill you, report researchers in the British Medical Journal's special Christmas issue.

For most people, it's probably safe to chuckle.

The paper's authors, two pharmacologists with a shared interest in humor, reviewed about 5,000 studies. They found that intense laughter can trigger fainting, asthma attacks, "protrusion of abdominal hernias," headaches, incontinence, jaw dislocation, and arrhythmia.

It's also a rare cause of Boerhaave's syndrome, a spontaneous hole in the esophagus that's more commonly the result of vomiting.

"We don't know how much laughter is safe," study author Robin E. Ferner of The University of Birmingham told The New York Times. "There's probably a U-shaped curve: laughter is good for you, but enormous amounts are bad, perhaps."

James Hamblin, a physician who covers health for The Atlantic, wrote a 2011 essay for Splitsider all about laughter and death. He noted that laughing very hard can also rupture an aneurysm or be a symptom of something dire, like a seizure or a stroke.

Still, while the harms of laughter are real, there's no need to worry if thinking about them induces a chuckle. "The benefit-harm balance," the BMJ authors conclude, "is probably favourable."