We all want to believe that laughter is good for what ails us, but the science backing that up is thin. Most studies have been small and have relied on self-reported assessments.

Still, a rollicking good guffaw can’t hurt. Or can it? There are rare instances of laughter prompting an asthma attack and even rarer instances of it triggering a stroke. And though this hasn’t been part of a formal study, one researcher speculates that if you’re surrounded by people laughing inappropriately—finding, say, a cockfight hilarious—it increases stress.

However, a few studies relying on laboratory testing do show some benefits.

“A good belly laugh leads to the release of endorphins from the brain,” says Michael Miller, director of the Center for Preventive Cardiology at the University of Maryland Medical Center in Baltimore.

That release sets off a cascade of heart-healthy biological events. Endorphins, pleasure-inducing neurotransmitters, activate receptors on the surface of the endothelium, the layer of flat cells lining blood vessels. That leads to the release of nitric oxide, which widens blood vessels—increasing blood flow, lessening inflammation, inhibiting platelet clumping, and reducing the formation of cholesterol plaque.

A 2005 study by Miller measured the blood flow of 20 volunteers before and after watching a funny movie and a sad movie. After the sad movie, blood flow was more restricted in 14 of the 20 viewers. But after the movie that made them laugh, average blood flow increased by 22 percent.

“The best laugh is one that brings tears to our eyes,” says Miller, author of Heal Your Heart: The Positive Emotions Prescription to Prevent and Reverse Heart Disease, scheduled for publication by Rodale Press in September. His prescription: at least 30 minutes of exercise at least three times a week—and 15 minutes of daily laughter.

You Have to Laugh Out Loud

Funding for laughter and humor research is low—so low that when Mary Bennett, director of the Western Kentucky University School of Nursing, wanted to look into the effect of laughter on the immune system, she found herself scrounging, asking other researchers for vials and other equipment from their labs. “It’s really hard to get taken seriously when you say you study laughter,” she says.

But her study of 33 healthy women, published in 2003, showed that those who laughed at a humorous movie had higher levels of natural killer cell activity, which increased their ability to fight off disease. However, the effect was seen only in the subjects who laughed out loud, not in those who quietly watched the comedy… see more


source: National Geographic News