This Is What Happens To Your Body When You Laugh

Remember the last time you had a really good laugh? We mean a really good hearty laugh — when something was so funny it caused your eyes to water and your sides to hurt, and you couldn't catch a breath? And you might have even peed yourself a little? (We won't tell.)

Having a good laugh has body-wide effects, from the brain to the legs, and places in between. And even though yawning is said to be contagious, laughing is actually highly contagious. As it spreads, it helps form, reinforce, and maintain social bonds in large groups, a University of Turku study found (via Science Daily). Because it fosters closeness between members of a group, laughter is believed to have been important in the evolution of humans becoming so social, according to The New York Times.

But aside from the social aspects of laughter, when you're doubling over with giggles and guffaws it just feels good. Read on to discover what happens to your body when you're struck by a fit of uncontrollable laughter.

Laughter has an effect on the brain in at least two ways. First, it's been shown to trigger the release of endorphins, neurochemicals that promote an overall sense of well-being, reduce stress, and diminish the perception of pain.

To test how people might react to pain after social laughter, Robin Dunbar, an evolutionary psychologist at Oxford University, conducted a study in which participants were shown different combinations of videos that were either funny (e.g., "The Simpsons"), neutral (pet training or golfing), or were meant to trigger good feelings, but not laughter (nature shows). Afterward, the participants were subjected to painful stimuli, such as a tightening blood pressure cuff on their arm (via The New York Times). The results showed that laughter increased pain resistance, which is typically used as an indicator of endorphin levels. Simply feeling good in a group did not affect endorphin levels or pain perception. 

Secondly, the entire cerebral cortex is involved in laughter. A study of the brain's electrical activity found that four-tenths of a second before we hear a punchline, a wave of electricity blankets the whole cerebral cortex. So all or most of our higher brain plays a part in laughter — maybe the left hemisphere works on the joke's verbal content while the right hemisphere attempts to figure out the incongruity underlying the humor, Peter Derks, professor of psychology at the College of William and Mary, told Psychology Today.

Do you cry when you laugh really hard? You have your brain to thank for that as well. One reason you shed tears while you're cracking up is due to the hypothalamus, the part of the brain responsible for emotion. Because the hypothalamus is so small, hearty laughing can trigger other emotional reactions in it as well, such as crying. And then there's the face you make when you're laughing. That scrunched expression puts pressure on your tear ducts, prompting tears to fall, according to Healthpointe Multi-Speciality and Orthopedic Healthcare in Los Angeles.

Laughing affects your heart too. It mimics exercise in the sense that it increases heart rate (by 10% to 20%) and 10 to 15 minutes of laughing could raise energy expenditure by 10 to 40 calories a day, according to Vanderbilt University Medical Center. That adds up to almost four pounds lost a year! Additionally, laughing can elicit the same natural high that occurs after a workout, and it can relieve physical tension. This muscle-relaxing effect can last up to an hour after a good hearty laugh (per The Thirty).

The immune system can't resist the positive effects of laughter either. Having a chuckle boosts the immune system's effectiveness by reducing the levels of cortisol — a stress hormone that weakens immune response — by speeding up the production of new immune cells, and by activating the natural killer cells that protect the body from invading microorganisms, according to Psychology Today.

Have you ever felt that your knees might give out from under you when you're laughing hard? The phrase "weak with laughter" is more than a figure of speech; it actually was observed in a study published in The Lancet (via The New York Times). Researchers in the Netherlands were examining a medical condition when they serendipitously noticed that laughter appears to trigger a reflex that causes many muscles in the body to collapse. The next time you post ROTFL, you may actually be doing so.

If you're a woman, you may also pee a little when having a good laugh, otherwise known as stress incontinence. During laughter, the pressure inside the belly increases and if the pelvic floor muscles are weak or fatigued, this pressure can cause them to fail at holding in urine, according to physical therapist Wendy Carels at Kinetic Physical Therapy and Wellness in Greenville, North Carolina.

It's so common that women may even giggle about the peeing itself. In fact, 25% to 45% of women of all ages reported incontinence in the last year, and it's twice as likely in women than men, according to The Daily. The rates increase with age and after giving birth. But just because peeing while laughing is so common, it doesn't mean it has to happen. There are treatments for it. So next time hilarity ensues, maybe you won't have to rush off to the bathroom.