Laughter Is OK Medicine, Unless It Kills You

Careful with the bedside banter, doctors. Before you put on your best Patch Adams impression, you might want to consider whether your attempts at humor will ease your patient's discomfort or give him a protruding hernia.

That's the conclusion of a review paper in the Christmas issue of BMJ that asks the jolly question of whether laughter can kill. The two authors, R. E. Ferner of the University of Birmingham and J. K. Aronson of Oxford University—no JK-ing, those are his real initials—take a tongue-in-cheek approach. They even give their research question an acronym: MIRTH (Methodical Investigation of Risibility, Therapeutic and Harmful).

Ferner and Aronson scoured medical literature for studies having to do with laughter. After "excluding papers on the Caribbean sponge Prosuberites laughlini and with authors called Laughing, Laughter, Laughton, or McLaughlin," they were left with three categories of study. One had to do with the benefits of laughter, one with its dangers, and the third with medical conditions that have laughter as a symptom.

Let's hear the bad news first. Laughter, according to various researchers, can lead to syncope (fainting), arrhythmia, and cardiac rupture. In asthmatics, laughing can trigger an attack. Laughing can even cause pneumothorax, a collapsed lung. People with cataplexy, a rare condition tied to narcolepsy, may suddenly lose all their muscle strength and collapse during a fit of laughter. An especially good laugh can make a person's hernia protrude, or dislocate someone's jaw.

Among the more pedestrian dangers, breathing in sharply when you start to laugh can make you choke. Laughing in someone's face can spread germs. And, of course, there's the danger of pee coming out when you laugh, which doctors call "giggle incontinence."

The authors also gathered a list of about three dozen medical conditions that have been reported—commonly or not—to cause laughter. These include epilepsy, brain tumors, multiple sclerosis, and kuru (a disease you are unlikely to contract unless you're a practicing cannibal).

Now for the good news. Laughter may increase your pain tolerance, reduce stiffness in the walls of your arteries, and even lower your risk of a heart attack. In patients with chronic obstructive pulmonary disease (COPD), laughter can improve lung function. Fifteen minutes of laughter reportedly burns 40 calories, which fitness-wise makes it similar to a very slow walk (or, according to Fitness magazine, barbecuing.)

Most strangely, one study used clowns to try to (indirectly) get women pregnant. Immediately after undergoing IVF, women were subjected to 12 to 15 minutes of entertainment by "a clown, dressed as a chef de cuisine." Among these women, 36 percent became pregnant, compared to just 20 percent in a control group.

Perhaps aspiring clowns themselves, the authors can't resist throwing in a few puns of their own: "Laughing fit to burst can cause cardiac rupture." "Perhaps surgical patients derive no advantage from being in stitches." "It remains to be seen whether...sick jokes make you ill, [or] dry wit causes dehydration." I'll give them the benefit of the doubt and assume that, knowing the potentially serious side effects of laughter, they chose to spare their audience the risk.


Image: Urban Combing (Ultrastar175g) (via Flickr)

R E Ferner, & J K Aronson (2013). Laughter and MIRTH (Methodical Investigation of Risibility, Therapeutic and Harmful): narrative synthesis. BMJ DOI: 10.1136/bmj.f7274

Are Your Gut Bacteria Vegetarian?

This spring, scientists announced that each person seems to have a signature set of gut bacteria, like a blood type for the microbiome. Their human subjects fell into three separate "enterotypes," each one representing a distinct microbial ecosystem. The enterotypes didn't correlate with subjects' age, gender, or nationality. But a new study has found something that does predict what enterotype you'll host: eating a plant- or animal-based diet.

Researchers surveyed 98 subjects about their diets, both recently and in the long term. They also took stool samples from their subjects. The scientists gave this portion of their study the very belabored acronym COMBO, for "Cross-sectional study Of diet and stool MicroBiOme composition."(It's not clear whether COMBO is meant to reference the combination of survey data and fecal data, or the resemblance a cheese-filled pretzel tube has to a cross-section of the colon.)

The researchers used these diet surveys to create profiles of subjects' nutrient intake. They also sequenced the DNA in subjects' stool samples to create profiles of their bacterial communities.

What they found was that subjects could be clustered into two bacterial ecosystems. One group's guts were dominated by bacteria in the genus Bacteroides; the others were dominated by Prevotella bacteria. (These match up with two of the three enterotypes described in the earlier study. In the current study, there was some evidence for the third enterotype the other authors had described--characterized by Ruminococcus bacteria--but in most statistical analyses this enterotype was merged with Bacteroides.)

Comparing enterotype data to dietary data, they saw a strong correlation between a person's bacterial type and his or her preferred nutrient sources. The Bacteroides enterotype showed up in people who consumed more animal proteins and fats. The Prevotella type, on the other hand, went along with higher consumption of carbohydrates and fiber--in other words, plants.

The second portion of the study was called CAFE, short for Controlled Feeding Experiment. You might notice that there's no A in the experiment's actual title--but that's fitting, given that the experiment was basically the opposite of a café. A patron in a café usually expects to choose food from a menu, whereas the 10 subjects in the CAFE experiment had to stay in the research center for 10 days and eat exactly what was put in front of them, no more or less. (This sounds more like a CAFO, or Concentrated Animal Feeding Operation, also called a factory farm.) Half the subjects were put on a diet that was high-fat/low-fiber, and the other half ate a low-fat/high-fiber diet. All subjects ate identical meals; the only difference between the two diets was in the proportions of foods on the plate.

Also unlike in a café, subjects had to provide daily stool samples to the researchers. All 10 subjects started out with the Bacteroides (high protein and fat) enterotype. Over the course of their 10-day diet, none of the high-fiber subjects switched over to the opposite enterotype. Even though their bacterial types seemed to be based on their long-term diets, a 10-day change in diet wasn't enough to seriously affect subjects' bacterial ecosystems.

The different diet did affect the members within each ecosystem, though. Within 24 hours of starting their new diet, subjects' bacterial populations shifted noticeably. So while a temporary change in diet may not permanently alter your enterotype, it could significantly change the balance of different microbes within that enterotype.

In their dietary surveys, the researchers found a few other factors that were tied to the balance of microbes in subjects' guts, but not to a particular enterotype. BMI was one unsurprising example. Others included red wine and aspartame consumption--suggesting either that aspartame kills off gut bacteria, or that something has actually evolved to live on it.

The earlier study, which used a smaller sample size, found no link between enterotype and nationality. But a larger sample size might be able to capture connections between gut bacteria and nationality that reflect different countries' dietary traditions. The current paper references a study that compared European children to children in the African nation of Burkina Faso. While European children tended to have the Bacteroides (animal nutrients) enterotype, the African children were more likely to have the plant-related Prevotella enterotype, reflecting their high-carbohydrate diet.

Increasingly, connections are cropping up between human health--both mental and physical--and the microbiome. We know very little about our relationship with our gut bacteria, but untangling more connections like this one will help us understand how to stay on good terms with them. In the future, keeping ourselves healthy may mean keeping our internal ecosystems well-fed.

Wu, G., Chen, J., Hoffmann, C., Bittinger, K., Chen, Y., Keilbaugh, S., Bewtra, M., Knights, D., Walters, W., Knight, R., Sinha, R., Gilroy, E., Gupta, K., Baldassano, R., Nessel, L., Li, H., Bushman, F., & Lewis, J. (2011). Linking Long-Term Dietary Patterns with Gut Microbial Enterotypes Science DOI: 10.1126/science.1208344

The Sniff Test for Mental Illness

Imagine a patient goes to see his general practitioner, complaining of exhaustion. He can't sleep, and he'd like a referral to a sleep clinic so he can get some answers. First, his doctor wants to administer a quick test. She holds a device like a felt-tipped pen just under her patient's nose and has him sniff. "Sure, I can smell that," he says. She gives him three pens and asks which one smells different from the other two. "They all smell like peppermint to me," the patient says. "Okay," the doctor says, "I'm referring you to a psychiatrist."

This type of test, if it exists someday, would take advantage of the fact that your brain's components aren't just responsible for one job apiece. For example, an area right above your eyeballs called the orbitofrontal cortex is involved in decision making and emotions--and your sense of smell. According to researchers in Belgium, a test of olfactory abilities might be able to alert doctors to an underlying condition such as depression, dementia, or schizophrenia.

Pierre Maurage and his colleagues studied a group of 20 alcoholics who were receiving treatment and hadn't drunk for at least two weeks. Each alcoholic was matched with a control: a person of the same age, sex, and education level who had no history of psychiatric problems or substance abuse.

Subjects took three kinds of tests. The first set of tests measured their olfactory abilities. Subjects were given pens to sniff; researchers assessed their sensitivity to different concentrations of odors, their ability to tell different odors apart, and whether they could correctly identify what they smelled.

Next, subjects took two cognitive tests. In one test, they looked at words on a screen and had to press a button to indicate whether each word was an animal or an object--but if they heard a beep, they had to stop themselves from answering the question. This is a test of general cognitive functioning that doesn't specifically involve the orbitofrontal cortex.

The third test was one that is known to activate the orbitofrontal cortex. Subjects had to view a series of pictures and say whether they'd seen them already or not. Later in the day, they repeated the test, and were asked to forget what they'd seen in the first test. If subjects had trouble remembering whether a picture was familiar because they'd seen it a few moments ago or earlier in the day, they were given a high "confabulation" score. Confabulation is the tendency to fill gaps in your memory with false events; it's a problem some alcoholics have.

Both groups of subjects, the alcoholics and the controls, scored the same in the general cognitive test. But in the confabulation test, alcoholics performed worse. They also did worse in the sniffing tests. Alcoholics didn't have an impaired sense of smell overall; they could detect scents at the same threshold as non-alcoholics. But they had a harder time identifying odors and telling two odors apart. This indicates that the problem isn't in the actual smelling, but in the brain's processing of smells.

So although the researchers weren't able to confirm their observations with brain scans, it seems that alcoholics had impaired brain functioning specifically in the orbitofrontal cortex. In addition to causing confabulation, this affected their performance on a smell test.

If this relationship proves to be reliable, it could give doctors a shortcut to test their patients' mental functioning. A sniff test given to alcoholics could reveal how likely they are to be experiencing memory gaps. Smell tests given to patients with other psychiatric disorders that affect olfaction (such as depression, dementia, anorexia, or schizophrenia) could provide clues as to what cognitive problems they're having--or whether certain brain areas are working just fine. And in other patients, a poor smelling score could suggest an undiagnosed mental illness. Since this study found a result in odor processing in the brain, though, and not subjects' ability to detect odors generally, you don't have to worry that a head cold will get you sent to therapy.

For now, doctors will have to rely on probing questions and physical exams rather than scented pens. And no one knows what was going on with that kid in your kindergarten class who couldn't stop sniffing the grape Mr. Sketch marker--though if smell tests are introduced in doctor's offices, one assumes he'll be thrilled.


Maurage, P., Callot, C., Chang, B., Philippot, P., Rombaux, P., & de Timary, P. (2011). Olfactory Impairment Is Correlated with Confabulation in Alcoholism: Towards a Multimodal Testing of Orbitofrontal Cortex PLoS ONE, 6 (8) DOI: 10.1371/journal.pone.0023190

The One Funny Thing

Most science is not hilarious. Science is slow, it involves repeating the same action tens or hundreds or thousands of times, and it often investigates deeply unfunny subjects such as cancer or polymer synthesis. That's why the rule of the One Funny Thing is such a relief.

The rule goes like this: If you read a paper all the way through, top to bottom, you have a good chance of finding something funny. It's usually hiding in the Methods section. Now, I can't vouch for the aforementioned cancer and materials science studies, and I admit the humor in most astronomy papers eludes me. But I always feel reassured to find something silly tucked away in an otherwise serious, peer-reviewed paper.

What follows is a collection of funny things. Some of them are from studies I've written about on this blog, in which case you can follow the link to get to the original story. Others are studies I've read for work. Going forward, when I cover a story that follows the rule, I'll label it with the "One Funny Thing" tag. Clicking that tag will take you back to this page, where I'll add the new tidbit at the top of the list.

Good to Know
On recruiting volunteers for a study about diet and gut bacteria:

To be eligible, participants were required to be free from any chronic gastrointestinal disease, cardiac disease, diabetes mellitus or immunodeficiency diseases, to have a normal bowel frequency (minimum once every 2 days, maximum 3 times per day)...

Sniffin' Sticks
To search for a correlation between people's olfactory abilities and the functioning of a certain brain area, researchers in Belgium started by giving their subjects a sniff quiz.

Orthonasal olfactory function was assessed by means of the standardized "Sniffin' Sticks" test. In this evaluation, odors are presented using felt-tip pens containing a tampon filled with four milliliters of liquid odorants. 

I wonder if the liquid odorants were blue, as in every Kotex commercial.

Mouse Refusal

In a study of people's intuitive geometric knowledge, researchers gave a group of five- and six-year-olds a test on a computer. 

Two additional children were excluded from the final sample in the lines intuition task, one because he was attending second grade despite his young age and the other because he refused to use the mouse of the computer.

Un-amenable Ostriches
Scientists studied the locomotion of ostriches by sticking motion-capture balls all over the birds' bodies. They started with five baby ostriches, reared them by hand, and spent eight months training the birds three to four times a week. After all this, only

[T]wo animals were amenable to the procedures required for full three-dimensional gait analysis.

Three out of five birds, that is, were totally untrainable. This might explain why more ostrich research isn't done. I've watched Animal Cops Houston. An ostrich that is not amenable to something will let you know by kicking you in the head.

Adverse Events
This is almost cheating because the whole paper is so funny. The authors asked whether wearing socks over your shoes made it safer to walk down an icy hill (and won and Ig Nobel award for their efforts). First, the researchers recruited passing university students:

In light of the observed behavior of pedestrians (often young men) at these sites on previous mornings, participants were asked to refrain from deliberately skidding or sliding.

As participants made their way down the hill, with or without external socks,

Assessors were also asked to document any falls and to comment on the demeanor of the participants during their descent (for example, "walked confidently," "clung to fences or parked cars," "crawled").

Finally, the authors conclude that the socks did help.

The only adverse events were short periods of embarrassment for the image-conscious.

Expelling the Plug
It's believed that homing pigeons navigate partly by smell. To find out whether the birds depended more on one nostril than the other (they did; it was the right), researchers took on the task of plugging pigeon nostrils. 

The evening before the experimental releases, one nostril of each of the...pigeons was plugged. The plugs were made with a small amount of paste (Xantopren®, Heraues Kulzer, Hanau, Germany), which turns into a solid rubbery plug after insertion into the nostril. The plugs were removed once the pigeons homed.

The pigeons may have objected.

From our preliminary observations, the pigeons are able to expel the plug within a few days.

Cautious Conclusion
A study of high-schoolers found that daylight saving time might negatively affect SAT scores. (Some test dates were immediately after clock changes, and teenagers like to sleep a lot.)

The cautious conclusion is that the daylight-saving time policy should possibly be even more controversial.

Yes, I'll say that's a cautious conclusion.

Rapid Scissoring
From a paper on whether lobsters can recognize each other before deciding whether to fight comes a handy scale of lobster aggression. On one end of the scale is "Retreat." Levels of aggression progress through

Rapid and direct head-first advance towards opponent(s) without hesitation, often with claws outstretched

to

Rapid scissoring motion with both claws at opponent

and finally

Contraction of the abdomen to propel animal backwards in an attempt to rip off opponent's appendage.

The authors reassure us:

The experiments comply with the current laws of Italy, the country in which they were done...We intended to separate the lobsters and consider the observation over if fights appeared to escalate to potentially damaging levels.

After the experiment, they froze all the lobsters to death anyway.

No Objective Way
A story about skunks and other stink-spraying animals also contained a helpful scale, this time measuring the degree to which an animal uses its anal gland secretions for defense, but I'll spare you the details. The authors quantified every possible aspect of each animal's coloration, habitat, and behavior. Some things couldn't be measured, though.

It is worth noting that several boldly colored species are quite pugnacious...however, we were unable to create an objective metric for ferocity. 

Similarly,

Although species that use anal gland defenses also vary in the noxiousness of the secretion, there was no objective way to score this.

I wish they had tried.