Marty Lederhandler / AP file

In this Nov. 9, 1967 file photo, U.S. President Lyndon B. Johnson and George Meany, president of AFL-CIO, laugh at a speaker's remark during the first annual Jewish Labor Committee Human Rights Awards dinner at the Sheraton in New York.

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This is no laughing matter (or maybe it is): A small British study has found that laughter can increase your tolerance of pain. It seems that cracking up in the company of other people releases endorphins, the same feel-good brain chemicals triggered while exercising.

Laughter is helpful when you're hurting because it's hard work for the body. A hearty, sustained laugh is a good workout for muscles in the chest and lungs, and this can trigger the release of endorphins to mask the pain, says Robin Dunbar, PhD, a professor of evolutionary psychology at Oxford University, who led the study. When endorphin levels increase, a person's pain threshold rise, he explains. 

For the study, published in the Proceedings of the Royal Society B, scientists ran a series of six different experiments in the lab and one in a real-world setting, during live stage performances at the Edinburgh Fringe Festival. Many of the tests were done in small groups because other research has shown that laughter is 30 times more likely to occur in a social situation than when you're alone.

In some studies, half of the volunteers watched a comedy video -- ranging from episodes of "South Park" and "Friends" to "Mr. Bean" and "The Simpsons" -- while the others viewed a documentary on dull stuff like golf instruction, pet training, or a nature show. 

Each participant's individual pain threshold was tested before and after watching the videos, using such pain-inducing techniques as an increasingly tighter blood pressure cuff around the upper arm or a frozen wine cooler sleeve placed on the forearm and held there until the person couldn't take it any longer. Pain tolerance was considered a proxy measure of endorphin levels.

Researchers also recorded the amount of time participants spent laughing. But polite titters wouldn't cut it; only relaxed social laughter that stretched smile muscles in the face counted.

Pain tolerance was shown to be higher in men and women who watched funny videos, but they stayed the same or were lower in those who didn't. Scientists were also able to tease out that a person's ability to handle more pain was due to the laughter itself and not just because it put someone in a better mood.

Laughter is definitely some of the best medicine for pain, says Dunbar. It seems that endorphins tune up the immune system, so triggering their release through laughter helps you recover from disease and allows the body to resist infection, he explains

Would some comic relief help those suffering from chronic pain? Presumably, the more you engage in social events that involve laughter, you'll be better able to bear chronic pain, Dunbar says.

"No doubt the pharmaceutical companies won't like it, but laughter would save on hospital bills," he points out.

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As a some-time stand-up comic, Robert Lynch wondered why some people in the audience howled with laugher, while others sat stony-faced. Research and anecdotal evidence have found that people look for friends and mates with senses of humor, but he couldn’t grasp why some people got it and others seemed puzzled.

“It had to be something pretty fundamental about humor,” says Lynch, a doctoral student in evolutionary anthropology at Rutgers, the State University of New Jersey.

At the time, his advisor and co-author, Robert Trivers, was writing a book about self-deception, so Lynch decided to look at how self-deception -- basically, lying to yourself -- influenced sense of humor. He found that the more someone practiced self-deception, the less likely they were to genuinely laugh.

Lynch asked 59 college students (33 female, 26 male) to watch a 28-minute video of comedian Bill Burr’s stand-up. (This is a departure; most humor research uses jokes from joke books, which, let’s face it, only people without senses of humor and your weird uncle find funny.) Each subject watched the show alone while the researchers videotaped the reactions. Participants also filled out a survey to reveal whether they practiced self-deception and then answered some additional questions about mood, extraversion, and whether they enjoyed the comedian.

“Humor is intrinsically difficult to study. Robert's genius was to measure  it precisely via FACS, a facial identification system that can isolate different kinds and intensities of laughter,” says Trivers, professor of anthropology and biological sciences at Rutgers University.

Lynch examined the videos and coded each person’s reaction using FACS, or facial action coding system, which links slight facial changes to emotions. He recorded the actions per frame, noting the duration and intensity of each. Specifically, he looked at the lips to see if students smiled with a Duchenne smile, which is an involuntary and genuine grin. Also, he watched the eyes. People can fake a guffaw or a smile, but FACS ensures he could tell if students genuinely smiled or forced it.   

“Real smiles come from the eyes,” Lynch says, noting it’s impossible to fake an authentic laugh.  

Self-deceivers were less likely to laugh at the stand-up comic than those who were more honest. Lynch suspects that it’s because comedians often joke about taboo topics, and those who are lying to themselves can’t chuckle because they feel it would be too revealing.  

 “[Laughter] is an honest, involuntary emotional signal and it is signaling enjoyment. People who are self-deceptive could be more concerned with honest signaling. It’s a little bit dangerous for them to be laughing because they don’t get it themselves and there are concealing the truth to themselves and they are concealing it to others,” Lynch says.  

The paper, “Self-deception inhibits laughter,” is available online at the journal Personality and Individual Differences. 

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• Your doc's sick sense of humor is good for your health
• We may hate laugh tracks -- but they work, studies show

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The joke sounds like a mordant New Yorker cartoon, or a crack from Dennis Leary’s stand-up routine: A pizza delivery guy lies dead from a gunshot just steps from his destination. The waiting customers find the pizza and one asks “How much do we think we should tip him?”

But this really happened to a real pizza delivery guy and a group of hospital doctors who ordered the pizza, leading one of those doctors to ask Northwestern University bioethicist Katie Watson a question: “Was it wrong to make the joke?”

Watson, writing in a report for the Hastings Center, a bioethics think tank in Garrison, New York, answers no. “To me, the butt of the doctors’ tip joke is not the patient. It’s death,” she writes in the report.

Gallows humor is a time-honored coping mechanism. Soldiers, emergency room doctors and nurses, reporters, cops, even families facing the imminent death of a loved one engage in gallows humor, much of it utterly unprintable here. One of the funniest people I know worked as a “death counselor” for the terminally ill and tragically injured, and it was amazing what she could do with material like stab wounds and brain cancer.

In the case of the doctors, when they found the pizza man, they struggled to save his life and failed. Yet they had a shift to work at the hospital and more patients to help. Cracking a joke, as crass as it may seem upon reflection, helped them do that.

“Doctors are not robotic systems for healthcare delivery,” Watson said in an interview. “They are human beings. Yet they are expected to behave as if vomit doesn’t smell, and death is not scary.”

Some of what Watson calls “backstage” humor -- jokes and stories told among doctors, or teachers in a teachers’ lounge, or war reporters in a bar -- is a way to relieve tension and excise demons.

Which is not to say it’s always OK. Watson believes doctors, or anybody else, should be guided by the thought of harm. Who will a joke hurt? Is the humor making somebody a punching bag when a doctor’s real anger is toward, say, his or her boss? Could future patients be harmed in any way?

Of course not all doctors, or reporters, or school teachers, or firefighters, want to publicize the fact that they make cracks behind closed doors at all. One surgeon, Watson said, “was upset with me for discussing it outside the healthcare profession. She worried it would make patients trust doctors less.”

To which we say -- nyuk, nyuk, nyuk – give us the doctor who laughs.

Follow msnbc.com contributor Brian Alexander on Twitter.

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Hahahaha, laughs the live studio audience watching NBC's new sitcom, "Whitney."

Two new fall TV shows premiering this week, "2 Broke Girls" on CBS and "Whitney" on NBC, are counting on an old-fashioned sitcom standby to help them get chuckles and ratings: the laugh track.

Some TV networks and producers may love to use laugh tracks, and some viewers have grown to accept them as part of a program's background noise, much like the music or special effects used in a drama. Others -- including many television critics -- loathe the made-for-TV mirth.

But no matter your opinion of the canned ha-ha's, shows continue to use them because they work! They're meant to make the audience at home feel like they're part of a bigger crowd sitting in a movie theater or at a comedy club.

"We're much more likely to laugh at something funny in the presence of other people," says Bill Kelley, a psychology professor at Dartmouth College in Hanover, N.H, who has studied the brain's response to humor. Hearing others laugh -- even if it's prerecorded -- can encourage us to chuckle and enjoy ourselves more. In fact, a 1974 study published in the Journal of Personality and Social Psychology showed that people were more likely to laugh at jokes that were followed by canned laughter.

Kelley's own research compared student's reactions to an episode of "Seinfeld," which has a laugh track, to those watching "The Simpsons," which lacks one. Brain scans suggested that people found the same things funny and the same regions of their brain lit up whether or not they heard others laughing.

While his findings may give reason to do away with a laugh track, Kelley still sees value in them. When done well, he says, they can give people pointers about what's funny and help them along. But when done poorly, he admits, you notice a laugh track and it seems unnatural and out of place. 

Some beloved shows, like "30 Rock," "Curb Your Enthusiasm," "Modern Family," "The Office" and "Glee," have said no to the laugh track, preferring the audience's authentic reactions to their humor and punch lines. They let viewers decide for themselves when and how much something tickles their funny bone.

But not all laugh tracks are created equal. Both "Whitney" and "2 Broke Girls" tape before a live studio audience and record the audience's giggles and guffaws. Even though they get a genuine human reaction to the show's jokes and humor, producers often "sweeten" a laugh track, meaning they edit it. 

Sound engineers might insert some chortles if a wisecrack fell flat or lengthen the time an audience spends cracking up. They may also tone down the woman who loudly cackles at the wrong times or the obnoxious guy who is perpetually in stitches.

For comedies that don't shoot live, such as "How I Met Your Mother," they rely on "canned laughter," a pre-recorded mix of tee-hees and chuckles that may sound phony. Hearing it may make you wish had a mute button for the synthetic snickers. 

Popular shows that currently dub in the yuks, whether they tape before a live audience or not, include "Two and a Half Men," "The Big Bang Theory" and "Mike & Molly." Past sitcom sensations, from "Seinfeld" and "Cheers" to "Friends" and "Frasier," also turned to some form of electronically enhanced giggles.

Do shows with TV laugh tracks make you yuk or say "yuck"? Can you tune them out or do they drive you crazy?

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Be careful how hard you laugh at some of this summer’s blockbuster comedies. "Bridesmaids," "Horrible Bosses" or "The Hangover" sequel could just be the death of you.

“Years ago, I went to see 'Raiders of the Lost Ark' with a friend and I thought I was going to die laughing,” says Jim Dailakis, a 41-year-old comedian from Queens, N.Y. “We had this brutal karate instructor who looked just like this little golden head that Harrison Ford holds up at one point. I saw that head and started howling like a girl. And then I couldn’t catch my breath and had to think of something else so I wouldn’t pass out.”

Dailakis, who says he’s usually goaded into uncontrollable laughing fits by his buddies, says he’s actually blacked out laughing over the years.

“The first time it happened, I thought I was going to die,” he says. “I was on my knees laughing, and then suddenly I couldn’t breathe. It was scary and freaky but I couldn’t stop laughing. And then I began to weep uncontrollably and I thought that was so hilarious, I went into another manic fit of laughter. My friend was laughing so hard, he had to leave the room.”

After that, Dailakis saw stars -- then passed out.

“The next thing I knew, I was lying down and looking up,” he says. “And I could still hear my friend laughing in the next room.”

According to Dr. Martin Samuels, professor of neurology at Harvard Medical School, blacking out while laughing may be related to over-breathing, and is probably not too dangerous.

“This is most likely benign and unlikely that it would lead to death,” he says.

But that doesn’t mean death doesn’t sometimes wear a smile. In the third century B.C., the Greek philosopher Chrysippus was said to have died laughing after getting his donkey drunk on wine. More recently, a Danish audiologist died laughing in 1989 while watching "A Fish Called Wanda." (It's also the subject of an old Monty Python sketch, in which a writer pens the "funniest joke in the world" -- and immediately dies.)

“Happy news is just as dangerous as sad news with regard to the risk of sudden death,” he says. “I have cases of people who died after hitting holes in one, after bowling perfect 300 games and upon hearing the words ‘Not Guilty.’ Death during sexual activity is also well known. Ecstasy, happiness and good news are definitely risky.”

Why would good news or happy circumstances put us at risk?  It’s all about that old fight-or-flight response, he says.

“Extreme excitement, whether that be sadness or happiness activates the part of the brain that’s responsible for the flight or fight response to threats in the wild,” he says. “This releases a natural chemical -- adrenaline -- which in large animals can be toxic to various organs, in particular the heart.”

As a result, extremely strong emotional states -- whether positive or negative -- can be harmful to the heart, on rare occasions causing an abnormal rhythm which can be lethal.

Dailakis says his laughter blackouts used to bother him, but now that he knows what to expect, he’s not worried.

“Afterward, I feel exhausted but so alive,” he says. “I wouldn’t change it for the world. Why should I go to a doctor? It’s obviously a natural thing. It would be like telling the doctor, ‘I get turned on really easily. Can you stop that?’”

When's the last time you laughed so hard you couldn't catch your breath? What happened? Leave a comment telling us about it.

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