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Whenever I took a tumble or scraped my knee as a child, my mother typically assessed the situation and then promptly tickled me, counseling, “Laughter is the best medicine.” This trick remains remarkably effective with my own boys and, to this day, YouTube videos of laughing babies or cats playing with printers still have the power to make me feel a bit better when I’m under the weather.

But while giggling is certainly a great distraction when you’re hurt or feeling low, I can’t help but wonder whether the old adage is true: Can laughter really have a positive impact on health?

There is a growing body of research indicating that a good guffaw may improve immune function, help lower blood pressure, boost mood and reduce stress and depression. And despite a dearth of more rigorous, long-term studies, the sum of these findings is compelling, says cardiologist Michael Miller, a professor at the University of Maryland School of Medicine who has researched the topic.

“We don’t have any clinical outcome evidence to show that laughter will reduce heart attacks or improve overall survival. However, we do have a number of studies that have shown that there is a potential upside, in terms of vascular benefits and also overall health,” he explains. “These findings certainly support laughter as a reasonable prescription for heart health and health in general, especially since there’s really no downside.”

A new study from Oxford University supports a long-held theory that laughter triggers an increase in endorphins, the brain chemicals that can help you feel good, distract you from pain and maybe deliver other health benefits.

The study reports on six experiments in which people watched television sitcoms or a live comedy performance, either alone or with others. The participants were then subjected to various measures that prompt discomfort, including wearing an ice-cold sleeve or a tight blood-pressure cuff and squatting against a wall for long periods. In all cases, laughing with buddies for just 15 minutes resulted in an average 10 percent increase in pain threshold. A change in affect alone — in other words, getting happy but not laughing out loud — did not have a significant impact on pain sensations.

According to lead author Robin Dunbar, an evolutionary anthropologist, these results back up prior research suggesting that people who laugh need less pain medication after surgery. She explains that if laughing “triggers endorphin activation, then it may have direct health benefits, because there is a possibility that endorphins help to ‘tune’ the immune system.”

Not just any laughter

Still, we’re not just talking about a snicker here and there. The key is that real, true, unforced laughter is “an energetic, stressful activity that stirs up all of our physiological systems … involving strong vocalization, an increase in heart rate and blood pressure and muscle contractions all over the body,” says Robert Provine, a neuroscientist at the University of Maryland Baltimore County and the author of “Laughter: A Scientific Investigation.”

He explains that modern laughter of the “ha-ha” variety evolved from the “pant-pant” of primates and early humans, which he says is “really the sound of rough-and-tumble play.” Indeed, the new Oxford study found that endorphins are released only when “we ‘laugh till it hurts,’” meaning we end up running out of breath or physically exhausted, says Dunbar. “It is only full belly laughs that do this, not polite titters.”